Interfaces

We provide a lot of generic interfaces to write our bundled and your own custom types.

These interfaces are designed:

  1. To be subclassed

  2. To provide abstract methods to implement in your own types

  3. To enforce correctness on final types

  4. To attach critical laws to be checked

We use Higher Kinded Types to define abstract methods.

Reading about interfaces will be the most useful if you plan to create your own containers.

General information

All the non-specific interfaces (e.g. MappableN, BindableN, ApplicativeN) can have Nth types, at the maximum of three possible types. What does this mean?

MappableN interface, for example, can have one, two or three possible types. See the example below:

>>> from typing import NoReturn

>>> from returns.interfaces.mappable import (
...    MappableN, Mappable1, Mappable2, Mappable3,
... )

>>> one_type: MappableN[int, NoReturn, NoReturn]
>>> two_types: MappableN[int, str, NoReturn]
>>> three_types: MappableN[int, str, bool]

>>> # We have a shortcut for each amount of arguments to reduce the boilerplate
>>> one_type: Mappable1[int]
>>> two_types: Mappable2[int, str]
>>> three_type: Mappable3[int, str, bool]

Naming convention

We follow a very specific naming convention in our interface names.

If interface does not depend on the number of types it works with and is always the same, we name it as is. For example, Equable is always the same and does not depend on the number of type arguments. We use adjectives to name these interfaces.

Secondly, if interface depends on the number of type arguments, it is named with N suffix in the end. It would always have numeric aliases for each number of arguments supported. For example, MappableN, Mappable1, Mappable2, and Mappable3.

The last criteria we have to decided on naming is “whether this interface always the same or it can have slight variations”? That’s why we have ResultLikeN and ResultBasedN interfaces. Because ResultBasedN has two extra methods compared to ResultLikeN. We use Like suffix for interfaces that describes some similar types. We use Based suffix for interfaces that descire almost concrete types.

Laws

Some interfaces define its laws as values. These laws can be viewed as tests that are attached to the specific interface.

We are able to check them of any type that implements a given interfaces with laws by our own check_all_laws hypothesis plugin.

In this docs we are going to describe each general interface and its laws.

Mappable

Something is considered mappable if we can map it using a function, generally map is a method that accepts a function.

An example in this library is Maybe, that implements the Mappable interface:

>>> from returns.maybe import Maybe, Some

>>> def can_be_mapped(string: str) -> str:
...     return string + '!'

>>> maybe_str: Maybe[str] = Some('example')
>>> assert maybe_str.map(can_be_mapped) == Some('example!')

MappableN interface helps us to create our own mappable container like Maybe.

>>> from typing import Callable, TypeVar

>>> from returns.interfaces.mappable import Mappable1
>>> from returns.primitives.hkt import SupportsKind1
>>> from returns.primitives.container import BaseContainer

>>> _NumberType = TypeVar('_NumberType')
>>> _NewNumberType = TypeVar('_NewNumberType')

>>> class Number(
...     BaseContainer,
...     SupportsKind1['Number', _NumberType],
...     Mappable1[_NumberType],
... ):
...     def __init__(self, inner_value: _NumberType) -> None:
...         super().__init__(inner_value)
...
...     def map(  # This method is required by Mappable
...         self,
...         function: Callable[[_NumberType], _NewNumberType]
...     ) -> 'Number[_NewNumberType]':
...         return Number(function(self._inner_value))

With our Number mappable class we can compose easily math functions with it.

>>> def my_math_function(number: int) -> int:
...     return number - 1

>>> number: Number[int] = Number(-41)
>>> assert number.map(my_math_function).map(abs) == Number(42)

Laws

To make sure your Mappable implementation is right, you can apply the Mappable laws on it to test.

  1. Identity Law: When we pass the identity function to the map method, the Mappable instance has to be the same, unchanged.

>>> from returns.functions import identity

>>> mappable_number: Number[int] = Number(1)
>>> assert mappable_number.map(identity) == Number(1)
  1. Associative Law: Given two functions, x and y, calling the map method with x function and after that calling with y function must have the same result if we compose them together.

>>> from returns.functions import compose

>>> def add_one(number: int) -> int:
...     return number + 1

>>> def multiply_by_ten(number: int) -> int:
...     return number * 10

>>> mappable_number: Number[int] = Number(9)
>>> assert mappable_number.map(
...    add_one,
... ).map(
...    multiply_by_ten,
... ) == mappable_number.map(
...     compose(add_one, multiply_by_ten),
... )

Bindable

Bindable is something that we can bind with a function. Like Maybe, so BindableN interface will help us to create our custom bindable.

>>> from typing import Callable, TypeVar

>>> from returns.interfaces.bindable import Bindable1
>>> from returns.primitives.hkt import SupportsKind1, Kind1, dekind
>>> from returns.primitives.container import BaseContainer

>>> _NumberType = TypeVar('_NumberType')
>>> _NewNumberType = TypeVar('_NewNumberType')

>>> class Number(
...     BaseContainer,
...     SupportsKind1['Number', _NumberType],
...     Bindable1[_NumberType],
... ):
...     def __init__(self, inner_value: _NumberType) -> None:
...         super().__init__(inner_value)
...
...     def bind(  # This method is required by Bindable
...         self,
...         function: Kind1[
...             'Number',
...             Callable[[_NumberType], 'Number[_NewNumberType]'],
...         ],
...     ) -> 'Number[_NewNumberType]':
...         return dekind(function(self._inner_value))

And here’s how we can use it:

>>> def double(arg: int) -> Number[int]:
...    return Number(arg * 2)

>>> number = Number(5)
>>> assert number.bind(double) == Number(10)

Applicative

Something is considered applicative if it is a functor already and, moreover, we can apply another container to it and construct a new value with .from_value method.

An example in this library is Maybe, that implements the Mappable and Applicative interfaces:

>>> from returns.maybe import Maybe, Some

>>> maybe_str = Maybe.from_value('example')
>>> maybe_func = Maybe.from_value(len)  # we use function as a value!

>>> assert maybe_str.apply(maybe_func) == Some(7)

As you see, apply takes a container with a function inside and applies it to the current value inside the container.

This way we really execute Maybe.from_value(len('example')).

ApplicativeN which is a subtype of MappableN interface helps us to create our own applicative container like Maybe.

>>> from typing import Callable, TypeVar

>>> from returns.interfaces.applicative import Applicative1
>>> from returns.primitives.hkt import SupportsKind1, Kind1, dekind
>>> from returns.primitives.container import BaseContainer

>>> _NumberType = TypeVar('_NumberType')
>>> _NewNumberType = TypeVar('_NewNumberType')

>>> class Number(
...     BaseContainer,
...     SupportsKind1['Number', _NumberType],
...     Applicative1[_NumberType],
... ):
...     def __init__(self, inner_value: _NumberType) -> None:
...         super().__init__(inner_value)
...
...     def map(  # This method is required by Mappable
...         self,
...         function: Callable[[_NumberType], _NewNumberType]
...     ) -> 'Number[_NewNumberType]':
...         return Number(function(self._inner_value))
...
...     def apply(  # This method is required by Applicative
...         self,
...         container: Kind1[
...             'Number',
...             Callable[[_NumberType], _NewNumberType],
...         ],
...     ) -> 'Number[_NewNumberType]':
...         return Number.from_value(
...             dekind(container._inner_value(self._inner_value)),
...         )
...
...     @classmethod
...     def from_value(  # This method is required by Applicative
...         cls,
...         inner_value: _NewNumberType,
...     ) -> 'Number[_NewNumberType]':
...         return Number(inner_value)

With our Number mappable class we can compose easily math functions with it.

>>> def my_math_function(number: int) -> int:
...     return number - 1

>>> number = Number(3)
>>> number_function = Number.from_value(my_math_function)

>>> assert number.apply(number_function) == Number(2)

Laws

To make sure your Applicative implementation is right, you can apply the Applicative laws on it to test.

  1. Identity Law: When we pass an applicative instance with wrapped identity function to the apply method, the Applicative has to be the same, unchanged.

>>> from returns.functions import identity

>>> applicative_number: Number[int] = Number(1)
>>> assert applicative_number.apply(
...     applicative_number.from_value(identity),
... ) == Number(1)
  1. Interchange Law: We can start our composition with both raw value and a function.

>>> def function(arg: int) -> int:
...     return arg + 1

>>> raw_value = 5

>>> assert Number.from_value(raw_value).apply(
...     Number.from_value(function),
... ) == Number.from_value(function).apply(
...     Number.from_value(lambda inner: inner(raw_value)),
... )
  1. Homomorphism Law: The homomorphism law says that applying a wrapped function to a wrapped value is the same as applying the function to the value in the normal way and then using .from_value on the result.

>>> def function(arg: int) -> int:
...     return arg + 1

>>> raw_value = 5

>>> assert Number.from_value(
...     function(raw_value),
... ) == Number.from_value(raw_value).apply(
...     Number.from_value(function),
... )
  1. Composition Law: Applying two functions twice is the same as applying their composition once.

>>> from returns.functions import compose

>>> def first(arg: int) -> int:
...     return arg * 2

>>> def second(arg: int) -> int:
...     return arg + 1

>>> instance = Number(5)
>>> assert instance.apply(
...     Number.from_value(compose(first, second)),
... ) == instance.apply(
...     Number.from_value(first),
... ).apply(
...     Number.from_value(second),
... )

Plus all laws from MappableN interface.

Container

ContainerN is a central piece of our library. It is an interface that combines ApplicativeN and BindableN together.

So, in other words: Container is an Apllicative that you can bind!

>>> from typing import Callable, TypeVar

>>> from returns.interfaces.container import Container1
>>> from returns.primitives.hkt import SupportsKind1, Kind1, dekind
>>> from returns.primitives.container import BaseContainer

>>> _NumberType = TypeVar('_NumberType')
>>> _NewNumberType = TypeVar('_NewNumberType')

>>> class Number(
...     BaseContainer,
...     SupportsKind1['Number', _NumberType],
...     Container1[_NumberType],
... ):
...     def __init__(self, inner_value: _NumberType) -> None:
...         super().__init__(inner_value)
...
...     def map(  # This method is required by Mappable
...         self,
...         function: Callable[[_NumberType], _NewNumberType]
...     ) -> 'Number[_NewNumberType]':
...         return Number(function(self._inner_value))
...
...     def bind(  # This method is required by Bindable
...         self,
...         function: Kind1[
...             'Number',
...             Callable[[_NumberType], 'Number[_NewNumberType]'],
...         ],
...     ) -> 'Number[_NewNumberType]':
...         return dekind(function(self._inner_value))
...
...     def apply(  # This method is required by Applicative
...         self,
...         container: Kind1[
...             'Number',
...             Callable[[_NumberType], _NewNumberType],
...         ],
...     ) -> 'Number[_NewNumberType]':
...         return Number.from_value(
...             container._inner_value(self._inner_value),
...         )
...
...     @classmethod
...     def from_value(  # This method is required by Applicative
...         cls,
...         inner_value: _NewNumberType,
...     ) -> 'Number[_NewNumberType]':
...         return Number(inner_value)

This code gives us an opportunity to use Number with map, apply, and bind as we already did in the examples above.

Laws

To make sure other people will be able to use your implementation, it should respect three new laws.

  1. Left Identity: If we bind a function to our bindable must have to be the same result as passing the value directly to the function.

>>> def can_be_bound(value: int) -> Number[int]:
...     return Number(value)

>>> assert Number.from_value(5).bind(can_be_bound) == can_be_bound(5)
  1. Right Identity: If we pass the bindable constructor through bind must have to be the same result as instantiating the bindable on our own.

>>> number = Number(2)
>>> assert number.bind(Number) == Number(2)
  1. Associative Law: Given two functions, x and y, calling the bind method with x function and after that calling with y function must have the same result if we bind with a function that passes the value to x and then bind the result with y.

>>> def minus_one(arg: int) -> Number[int]:
...     return Number(arg - 1)

>>> def half(arg: int) -> Number[int]:
...     return Number(arg // 2)

>>> number = Number(9)
>>> assert number.bind(minus_one).bind(half) == number.bind(
...    lambda value: minus_one(value).bind(half),
... )

Plus all laws from MappableN and ApplicativeN interfaces.

More!

We have way more interfaces with different features! We have covered all of them in the technical docs.

So, use them to enforce type-safety of your own containers.

Specific interfaces

We also have a whole package of different specific interfaces that will help you to create containers based on our internal types, like Result.

FAQ

Why do you have general and specific interfaces?

We have .interfaces.* types that can be applied to any possible type. There’s nothing they know about other types or returns package.

We also have a special .interfaces.specific package where we have types that know about other types in returns.

For example, MappableN from .interfaces only knows about .map method. It does not require anything else.

But, ResultLikeN from .interfaces.specific.result does require to have .bind_result method which relies on our Result type.

That’s the only difference. Build your own types with any of those interfaces.

Why some interfaces do not have type alias for 1 or 2 type arguments?

Some types like ResultLikeN do not have type aliases for one type argument in a form of ResultLike1.

Why does Mappable1 exists and ResultLike1 does not?

Because Mappable1 does make sense. But, ResultLike1 requires at least two (value and error) types to exist. The same applies for ReaderLike1 and ReaderResultLike1 and ReaderResultLike2.

We don’t support type aliases for types that won’t make sense.

What’s the difference between MappableN and BindableN?

While MappableN you have to pass a pure function, like:

>>> def can_be_mapped(string: str) -> str:
...     return string

with Bindable we have to pass a function that returns another container:

>>> from returns.maybe import Maybe

>>> def can_be_bound(string: str) -> Maybe[str]:
...     return Some(string + '!')

The main difference is the return type. The consequence of this is big! BindableN allows to change the container type. While MappableN cannot do that.

So, Some.bind(function) can be evaluated to both Some and Nothing. While Some.map(function) will always stay as Some.

What is the difference between ResultLikeN and ResultBasedN?

ResultLikeN is just an intention of having a result (e.g. FutureResult), it’s not the result yet. While ResultBasedN is a concrete result (e.g. IOResult), it has the desired result value.

Because of this difference between them is why we can’t unwrap a ResultLikeN container, it does not have the real result yet.

See the example below using FutureResult to get a IOResult:

>>> import anyio
>>> from returns.future import FutureResult
>>> from returns.interfaces.specific.future_result import FutureResultBasedN
>>> from returns.interfaces.specific.ioresult import (
...    IOResultBasedN,
...    IOResultLikeN,
... )
>>> from returns.interfaces.specific.result import ResultLikeN, ResultBasedN
>>> from returns.io import IOSuccess, IOResult
>>> from returns.result import Success, Result

>>> async def coro(arg: int) -> Result[int, str]:
...     return Success(arg + 1)

>>> # `result_like` does not have the result we want (Result[int, str])
>>> # it's just the intention of having one,
>>> # we have to await it to get the real result
>>> result_like: FutureResult[int, str] = FutureResult(coro(1))
>>> assert isinstance(result_like, FutureResultBasedN)
>>> assert isinstance(result_like, IOResultLikeN)
>>> assert isinstance(result_like, ResultLikeN)

>>> # `anyio.run(...)` will await our coroutine and give the real result to us
>>> result: IOResult[int, str] = anyio.run(result_like.awaitable)
>>> assert isinstance(result, IOResultBasedN)
>>> assert isinstance(result, ResultLikeN)

>>> # Compare it with the real result:
>>> assert isinstance(Success(1), ResultBasedN)

Note

The same difference applies to all *ResultLikeN vs *ResultBasedN (e.g. IOResultLikeN and IOResultBasedN)

API Reference

Overview

Here’s a full overview of all our interfaces:

classDiagram ContainerN <|-- ReaderLike2 Lawful <|-- MaybeLikeN Lawful <|-- ApplicativeN FutureResultLikeN <|-- FutureResultBasedN Contextable <|-- CallableReader2 ContainerN <|-- IOLikeN Generic <|-- AwaitableFutureN Lawful <|-- ReaderResultBasedN Unwrappable <|-- MaybeBasedN Equable <|-- UnwrappableResult Equable <|-- IOBasedN LawSpecDef <|-- _SingleFailableLawSpec BindableN <|-- ContainerN IOBasedN <|-- IOResultBasedN Lawful <|-- MappableN AwaitableFutureN <|-- FutureBasedN ReaderResultLikeN <|-- ReaderResultBasedN FailableN <|-- SingleFailableN CallableReader3 <|-- ReaderResultBasedN Lawful <|-- DiverseFailableN Lawful <|-- ReaderBased2 UnwrappableResult <|-- IOResultBasedN ReaderLike3 <|-- CallableReader3 AltableN <|-- BiMappableN Generic <|-- LashableN Generic <|-- Unwrappable LashableN <|-- FailableN MappableN <|-- BiMappableN SwappableN <|-- DiverseFailableN IOResultLikeN <|-- FutureResultLikeN Contextable <|-- CallableReader3 ReaderIOResultLikeN <|-- ReaderIOResultBasedN DiverseFailableN <|-- ResultLikeN ReaderIOResultLikeN <|-- ReaderFutureResultLikeN ReaderLike3 <|-- ReaderResultLikeN ResultLikeN <|-- ReaderResultLikeN FutureResultLikeN <|-- ReaderFutureResultLikeN Lawful <|-- AltableN Unwrappable <|-- UnwrappableResult ReaderResultLikeN <|-- ReaderIOResultLikeN LawSpecDef <|-- _LawSpec IOLikeN <|-- FutureLikeN FailableN <|-- DiverseFailableN ReaderLike2 <|-- CallableReader2 Lawful <|-- ReaderFutureResultBasedN ContainerN <|-- FailableN FutureLikeN <|-- FutureBasedN MaybeLikeN <|-- MaybeBasedN FutureLikeN <|-- FutureResultLikeN ContainerN <|-- ReaderLike3 IOLikeN <|-- IOBasedN Lawful <|-- ReaderIOResultBasedN ResultLikeN <|-- UnwrappableResult CallableReader2 <|-- ReaderBased2 IOResultLikeN <|-- ReaderIOResultLikeN CallableReader3 <|-- ReaderFutureResultBasedN IOResultLikeN <|-- IOResultBasedN LawSpecDef <|-- _FailableLawSpec FutureBasedN <|-- FutureResultBasedN IOLikeN <|-- IOResultLikeN Lawful <|-- ContainerN Generic <|-- BindableN ResultLikeN <|-- IOResultLikeN Lawful <|-- FailableN CallableReader3 <|-- ReaderIOResultBasedN LawSpecDef <|-- _DiverseFailableLawSpec ReaderFutureResultLikeN <|-- ReaderFutureResultBasedN SingleFailableN <|-- MaybeLikeN Equable <|-- MaybeBasedN Generic <|-- Contextable UnwrappableResult <|-- ResultBasedN MappableN <|-- ApplicativeN ApplicativeN <|-- ContainerN

Let’s review it one by one.

Equable

classDiagram LawSpecDef <|-- _LawSpec Lawful <|-- Equable
class _LawSpec[source]

Bases: LawSpecDef

Equality laws.

Description: https://bit.ly/34D40iT

static reflexive_law(first)[source]

Value should be equal to itself.

Parameters:

first (TypeVar(_EqualType, bound= Equable)) –

Return type:

None

static symmetry_law(first, second)[source]

If A == B then B == A.

Parameters:
  • first (TypeVar(_EqualType, bound= Equable)) –

  • second (TypeVar(_EqualType, bound= Equable)) –

Return type:

None

static transitivity_law(first, second, third)[source]

If A == B and B == C then A == C.

Parameters:
  • first (TypeVar(_EqualType, bound= Equable)) –

  • second (TypeVar(_EqualType, bound= Equable)) –

  • third (TypeVar(_EqualType, bound= Equable)) –

Return type:

None

class Equable[source]

Bases: Lawful[Equable]

Interface for types that can be compared with real values.

Not all types can, because some don’t have the value at a time: - Future has to be awaited to get the value - Reader has to be called to get the value

_laws: ClassVar[Sequence[Law]] = (<returns.primitives.laws.Law1 object>, <returns.primitives.laws.Law2 object>, <returns.primitives.laws.Law3 object>)

Some classes and interfaces might have laws, some might not have any.

abstract equals(other)[source]

Type-safe equality check for values of the same type.

Parameters:
  • self (TypeVar(_EqualType, bound= Equable)) –

  • other (TypeVar(_EqualType, bound= Equable)) –

Return type:

bool

Mappable

classDiagram LawSpecDef <|-- _LawSpec Lawful <|-- MappableN
class _LawSpec[source]

Bases: LawSpecDef

Mappable or functor laws.

https://en.wikibooks.org/wiki/Haskell/The_Functor_class#The_functor_laws

static identity_law(mappable)[source]

Mapping identity over a value must return the value unchanged.

Parameters:

mappable (MappableN[TypeVar(_FirstType), TypeVar(_SecondType), TypeVar(_ThirdType)]) –

Return type:

None

static associative_law(mappable, first, second)[source]

Mapping twice or mapping a composition is the same thing.

Parameters:
  • mappable (MappableN[TypeVar(_FirstType), TypeVar(_SecondType), TypeVar(_ThirdType)]) –

  • first (Callable[[TypeVar(_FirstType)], TypeVar(_NewType1)]) –

  • second (Callable[[TypeVar(_NewType1)], TypeVar(_NewType2)]) –

Return type:

None

class MappableN[source]

Bases: Generic[_FirstType, _SecondType, _ThirdType], Lawful[MappableN[_FirstType, _SecondType, _ThirdType]]

Allows to chain wrapped values in containers with regular functions.

Behaves like a functor.

_laws: ClassVar[Sequence[Law]] = (<returns.primitives.laws.Law1 object>, <returns.primitives.laws.Law3 object>)

Some classes and interfaces might have laws, some might not have any.

abstract map(function)[source]

Allows to run a pure function over a container.

Parameters:
  • self (TypeVar(_MappableType, bound= MappableN)) –

  • function (Callable[[TypeVar(_FirstType)], TypeVar(_UpdatedType)]) –

Return type:

KindN[TypeVar(_MappableType, bound= MappableN), TypeVar(_UpdatedType), TypeVar(_SecondType), TypeVar(_ThirdType)]

Mappable1

Type alias for kinds with one type argument.

alias of MappableN[_FirstType, NoReturn, NoReturn]

Mappable2

Type alias for kinds with two type arguments.

alias of MappableN[_FirstType, _SecondType, NoReturn]

Mappable3

Type alias for kinds with three type arguments.

alias of MappableN[_FirstType, _SecondType, _ThirdType]

Bindable

classDiagram Generic <|-- BindableN
class BindableN[source]

Bases: Generic[_FirstType, _SecondType, _ThirdType]

Represents a “context” in which calculations can be executed.

Bindable allows you to bind together a series of calculations while maintaining the context of that specific container.

In contrast to returns.interfaces.lashable.LashableN, works with the first type argument.

abstract bind(function)[source]

Applies ‘function’ to the result of a previous calculation.

And returns a new container.

Parameters:
  • self (TypeVar(_BindableType, bound= BindableN)) –

  • function (Callable[[TypeVar(_FirstType)], KindN[TypeVar(_BindableType, bound= BindableN), TypeVar(_UpdatedType), TypeVar(_SecondType), TypeVar(_ThirdType)]]) –

Return type:

KindN[TypeVar(_BindableType, bound= BindableN), TypeVar(_UpdatedType), TypeVar(_SecondType), TypeVar(_ThirdType)]

Bindable1

Type alias for kinds with one type argument.

alias of BindableN[_FirstType, NoReturn, NoReturn]

Bindable2

Type alias for kinds with two type arguments.

alias of BindableN[_FirstType, _SecondType, NoReturn]

Bindable3

Type alias for kinds with three type arguments.

alias of BindableN[_FirstType, _SecondType, _ThirdType]

Applicative

classDiagram LawSpecDef <|-- _LawSpec Lawful <|-- ApplicativeN MappableN <|-- ApplicativeN
class _LawSpec[source]

Bases: LawSpecDef

Applicative mappable laws.

Definition: https://bit.ly/3hC8F8E Discussion: https://bit.ly/3jffz3L

static identity_law(container)[source]

Identity law.

If we apply wrapped identity function to a container, nothing happens.

Parameters:

container (ApplicativeN[TypeVar(_FirstType), TypeVar(_SecondType), TypeVar(_ThirdType)]) –

Return type:

None

static interchange_law(raw_value, container, function)[source]

Interchange law.

Basically we check that we can start our composition with both raw_value and function.

Great explanation: https://stackoverflow.com/q/27285918/4842742

Parameters:
  • raw_value (TypeVar(_FirstType)) –

  • container (ApplicativeN[TypeVar(_FirstType), TypeVar(_SecondType), TypeVar(_ThirdType)]) –

  • function (Callable[[TypeVar(_FirstType)], TypeVar(_NewType1)]) –

Return type:

None

static homomorphism_law(raw_value, container, function)[source]

Homomorphism law.

The homomorphism law says that applying a wrapped function to a wrapped value is the same as applying the function to the value in the normal way and then using .from_value on the result.

Parameters:
  • raw_value (TypeVar(_FirstType)) –

  • container (ApplicativeN[TypeVar(_FirstType), TypeVar(_SecondType), TypeVar(_ThirdType)]) –

  • function (Callable[[TypeVar(_FirstType)], TypeVar(_NewType1)]) –

Return type:

None

static composition_law(container, first, second)[source]

Composition law.

Applying two functions twice is the same as applying their composition once.

Parameters:
  • container (ApplicativeN[TypeVar(_FirstType), TypeVar(_SecondType), TypeVar(_ThirdType)]) –

  • first (Callable[[TypeVar(_FirstType)], TypeVar(_NewType1)]) –

  • second (Callable[[TypeVar(_NewType1)], TypeVar(_NewType2)]) –

Return type:

None

class ApplicativeN[source]

Bases: MappableN[_FirstType, _SecondType, _ThirdType], Lawful[ApplicativeN[_FirstType, _SecondType, _ThirdType]]

Allows to create unit containers from raw values and to apply wrapped funcs.

_laws: ClassVar[Sequence[Law]] = (<returns.primitives.laws.Law1 object>, <returns.primitives.laws.Law3 object>, <returns.primitives.laws.Law3 object>, <returns.primitives.laws.Law3 object>)

Some classes and interfaces might have laws, some might not have any.

abstract apply(container)[source]

Allows to apply a wrapped function over a container.

Parameters:
  • self (TypeVar(_ApplicativeType, bound= ApplicativeN)) –

  • container (KindN[TypeVar(_ApplicativeType, bound= ApplicativeN), Callable[[TypeVar(_FirstType)], TypeVar(_UpdatedType)], TypeVar(_SecondType), TypeVar(_ThirdType)]) –

Return type:

KindN[TypeVar(_ApplicativeType, bound= ApplicativeN), TypeVar(_UpdatedType), TypeVar(_SecondType), TypeVar(_ThirdType)]

abstract classmethod from_value(inner_value)[source]

Unit method to create new containers from any raw value.

Parameters:
  • cls (Type[TypeVar(_ApplicativeType, bound= ApplicativeN)]) –

  • inner_value (TypeVar(_UpdatedType)) –

Return type:

KindN[TypeVar(_ApplicativeType, bound= ApplicativeN), TypeVar(_UpdatedType), TypeVar(_SecondType), TypeVar(_ThirdType)]

Applicative1

Type alias for kinds with one type argument.

alias of ApplicativeN[_FirstType, NoReturn, NoReturn]

Applicative2

Type alias for kinds with two type arguments.

alias of ApplicativeN[_FirstType, _SecondType, NoReturn]

Applicative3

Type alias for kinds with three type arguments.

alias of ApplicativeN[_FirstType, _SecondType, _ThirdType]

Altable

classDiagram LawSpecDef <|-- _LawSpec Lawful <|-- AltableN
class _LawSpec[source]

Bases: LawSpecDef

Mappable or functor laws.

https://en.wikibooks.org/wiki/Haskell/The_Functor_class#The_functor_laws

static identity_law(altable)[source]

Mapping identity over a value must return the value unchanged.

Parameters:

altable (AltableN[TypeVar(_FirstType), TypeVar(_SecondType), TypeVar(_ThirdType)]) –

Return type:

None

static associative_law(altable, first, second)[source]

Mapping twice or mapping a composition is the same thing.

Parameters:
  • altable (AltableN[TypeVar(_FirstType), TypeVar(_SecondType), TypeVar(_ThirdType)]) –

  • first (Callable[[TypeVar(_SecondType)], TypeVar(_NewType1)]) –

  • second (Callable[[TypeVar(_NewType1)], TypeVar(_NewType2)]) –

Return type:

None

class AltableN[source]

Bases: Generic[_FirstType, _SecondType, _ThirdType], Lawful[AltableN[_FirstType, _SecondType, _ThirdType]]

Modifies the second type argument with a pure function.

_laws: ClassVar[Sequence[Law]] = (<returns.primitives.laws.Law1 object>, <returns.primitives.laws.Law3 object>)

Some classes and interfaces might have laws, some might not have any.

abstract alt(function)[source]

Allows to run a pure function over a container.

Parameters:
  • self (TypeVar(_AltableType, bound= AltableN)) –

  • function (Callable[[TypeVar(_SecondType)], TypeVar(_UpdatedType)]) –

Return type:

KindN[TypeVar(_AltableType, bound= AltableN), TypeVar(_FirstType), TypeVar(_UpdatedType), TypeVar(_ThirdType)]

Altable2

Type alias for kinds with two type arguments.

alias of AltableN[_FirstType, _SecondType, NoReturn]

Altable3

Type alias for kinds with three type arguments.

alias of AltableN[_FirstType, _SecondType, _ThirdType]

BiMappable

classDiagram AltableN <|-- BiMappableN MappableN <|-- BiMappableN
class BiMappableN[source]

Bases: MappableN[_FirstType, _SecondType, _ThirdType], AltableN[_FirstType, _SecondType, _ThirdType]

Allows to change both types of a container at the same time.

Uses .map to change first type and .alt to change second type.

BiMappable2

Type alias for kinds with two type arguments.

alias of BiMappableN[_FirstType, _SecondType, NoReturn]

BiMappable3

Type alias for kinds with three type arguments.

alias of BiMappableN[_FirstType, _SecondType, _ThirdType]

Swappable

classDiagram LawSpecDef <|-- _LawSpec Lawful <|-- SwappableN BiMappableN <|-- SwappableN
class _LawSpec[source]

Bases: LawSpecDef

Laws for SwappableN type.

static double_swap_law(container)[source]

Swaaping container twice.

It ensure that we get the initial value back. In other words, swapping twice does nothing.

Parameters:

container (SwappableN[TypeVar(_FirstType), TypeVar(_SecondType), TypeVar(_ThirdType)]) –

Return type:

None

class SwappableN[source]

Bases: BiMappableN[_FirstType, _SecondType, _ThirdType], Lawful[SwappableN[_FirstType, _SecondType, _ThirdType]]

Interface that allows swapping first and second type values.

_laws: ClassVar[Sequence[Law]] = (<returns.primitives.laws.Law1 object>,)

Some classes and interfaces might have laws, some might not have any.

abstract swap()[source]

Swaps first and second types in SwappableN.

Parameters:

self (TypeVar(_SwappableType, bound= SwappableN)) –

Return type:

KindN[TypeVar(_SwappableType, bound= SwappableN), TypeVar(_SecondType), TypeVar(_FirstType), TypeVar(_ThirdType)]

Swappable2

Type alias for kinds with two type arguments.

alias of SwappableN[_FirstType, _SecondType, NoReturn]

Swappable3

Type alias for kinds with three type arguments.

alias of SwappableN[_FirstType, _SecondType, _ThirdType]

Lashable

classDiagram Generic <|-- LashableN
class LashableN[source]

Bases: Generic[_FirstType, _SecondType, _ThirdType]

Represents a “context” in which calculations can be executed.

Rescueable allows you to bind together a series of calculations while maintaining the context of that specific container.

In contrast to returns.interfaces.bindable.BinbdaleN, works with the second type value.

abstract lash(function)[source]

Applies ‘function’ to the result of a previous calculation.

And returns a new container.

Parameters:
  • self (TypeVar(_LashableType, bound= LashableN)) –

  • function (Callable[[TypeVar(_SecondType)], KindN[TypeVar(_LashableType, bound= LashableN), TypeVar(_FirstType), TypeVar(_UpdatedType), TypeVar(_ThirdType)]]) –

Return type:

KindN[TypeVar(_LashableType, bound= LashableN), TypeVar(_FirstType), TypeVar(_UpdatedType), TypeVar(_ThirdType)]

Lashable2

Type alias for kinds with two type arguments.

alias of LashableN[_FirstType, _SecondType, NoReturn]

Lashable3

Type alias for kinds with three type arguments.

alias of LashableN[_FirstType, _SecondType, _ThirdType]

Unwrappable

classDiagram Generic <|-- Unwrappable
class Unwrappable[source]

Bases: Generic[_FirstType, _SecondType]

Represents containers that can unwrap and return its wrapped value.

There are no aliases or UnwrappableN for Unwrappable interface. Because it always uses two and just two types.

Not all types can be Unwrappable because we do require to raise UnwrapFailedError if unwrap is not possible.

abstract unwrap()[source]

Custom magic method to unwrap inner value from container.

Should be redefined for ones that actually have values. And for ones that raise an exception for no values.

Note

As a part of the contract, failed unwrap calls must raise returns.primitives.exceptions.UnwrapFailedError exception.

This method is the opposite of failure().

Parameters:

self (TypeVar(_UnwrappableType, bound= Unwrappable)) –

Return type:

TypeVar(_FirstType)

abstract failure()[source]

Custom magic method to unwrap inner value from the failed container.

Note

As a part of the contract, failed failure calls must raise returns.primitives.exceptions.UnwrapFailedError exception.

This method is the opposite of unwrap().

Parameters:

self (TypeVar(_UnwrappableType, bound= Unwrappable)) –

Return type:

TypeVar(_SecondType)

Container

classDiagram LawSpecDef <|-- _LawSpec BindableN <|-- ContainerN Lawful <|-- ContainerN ApplicativeN <|-- ContainerN
class _LawSpec[source]

Bases: LawSpecDef

Container laws.

Definition: https://wiki.haskell.org/Monad_laws Good explanation: https://bit.ly/2Qsi5re

static left_identity_law(raw_value, container, function)[source]

Left identity.

The first law states that if we take a value, put it in a default context with return and then feed it to a function by using bind, it’s the same as just taking the value and applying the function to it.

Parameters:
  • raw_value (TypeVar(_FirstType)) –

  • container (ContainerN[TypeVar(_FirstType), TypeVar(_SecondType), TypeVar(_ThirdType)]) –

  • function (Callable[[TypeVar(_FirstType)], KindN[ContainerN, TypeVar(_NewType1), TypeVar(_SecondType), TypeVar(_ThirdType)]]) –

Return type:

None

static right_identity_law(container)[source]

Right identity.

The second law states that if we have a container value and we use bind to feed it to .from_value, the result is our original container value.

Parameters:

container (ContainerN[TypeVar(_FirstType), TypeVar(_SecondType), TypeVar(_ThirdType)]) –

Return type:

None

static associative_law(container, first, second)[source]

Associativity law.

The final monad law says that when we have a chain of container functions applications with bind, it shouldn’t matter how they’re nested.

Parameters:
  • container (ContainerN[TypeVar(_FirstType), TypeVar(_SecondType), TypeVar(_ThirdType)]) –

  • first (Callable[[TypeVar(_FirstType)], KindN[ContainerN, TypeVar(_NewType1), TypeVar(_SecondType), TypeVar(_ThirdType)]]) –

  • second (Callable[[TypeVar(_NewType1)], KindN[ContainerN, TypeVar(_NewType2), TypeVar(_SecondType), TypeVar(_ThirdType)]]) –

Return type:

None

class ContainerN[source]

Bases: ApplicativeN[_FirstType, _SecondType, _ThirdType], BindableN[_FirstType, _SecondType, _ThirdType], Lawful[ContainerN[_FirstType, _SecondType, _ThirdType]]

Handy alias for types with .bind, .map, and .apply methods.

Should be a base class for almost any containers you write.

_laws: ClassVar[Sequence[Law]] = (<returns.primitives.laws.Law3 object>, <returns.primitives.laws.Law1 object>, <returns.primitives.laws.Law3 object>)

Some classes and interfaces might have laws, some might not have any.

Container1

Type alias for kinds with one type argument.

alias of ContainerN[_FirstType, NoReturn, NoReturn]

Container2

Type alias for kinds with two type arguments.

alias of ContainerN[_FirstType, _SecondType, NoReturn]

Container3

Type alias for kinds with three type arguments.

alias of ContainerN[_FirstType, _SecondType, _ThirdType]

Failable

classDiagram FailableN <|-- SingleFailableN Lawful <|-- DiverseFailableN FailableN <|-- DiverseFailableN Lawful <|-- FailableN ContainerN <|-- FailableN LawSpecDef <|-- _DiverseFailableLawSpec SwappableN <|-- DiverseFailableN LashableN <|-- FailableN LawSpecDef <|-- _SingleFailableLawSpec LawSpecDef <|-- _FailableLawSpec
class _FailableLawSpec[source]

Bases: LawSpecDef

Failable laws.

We need to be sure that .lash won’t lash success types.

static lash_short_circuit_law(raw_value, container, function)[source]

Ensures that you cannot lash a success.

Parameters:
  • raw_value (TypeVar(_FirstType)) –

  • container (FailableN[TypeVar(_FirstType), TypeVar(_SecondType), TypeVar(_ThirdType)]) –

  • function (Callable[[TypeVar(_SecondType)], KindN[FailableN, TypeVar(_FirstType), TypeVar(_NewFirstType), TypeVar(_ThirdType)]]) –

Return type:

None

class FailableN[source]

Bases: ContainerN[_FirstType, _SecondType, _ThirdType], LashableN[_FirstType, _SecondType, _ThirdType], Lawful[FailableN[_FirstType, _SecondType, _ThirdType]]

Base type for types that can fail.

It is a raw type and should not be used directly. Use SingleFailableN and DiverseFailableN instead.

_laws: ClassVar[Sequence[Law]] = (<returns.primitives.laws.Law3 object>,)

Some classes and interfaces might have laws, some might not have any.

Failable2

Type alias for kinds with two type arguments.

alias of FailableN[_FirstType, _SecondType, NoReturn]

Failable3

Type alias for kinds with three type arguments.

alias of FailableN[_FirstType, _SecondType, _ThirdType]

class _SingleFailableLawSpec[source]

Bases: LawSpecDef

Single Failable laws.

We need to be sure that .map and .bind works correctly for empty property.

static map_short_circuit_law(container, function)[source]

Ensures that you cannot map from the empty property.

Parameters:
  • container (SingleFailableN[TypeVar(_FirstType), TypeVar(_SecondType), TypeVar(_ThirdType)]) –

  • function (Callable[[TypeVar(_FirstType)], TypeVar(_NewFirstType)]) –

Return type:

None

static bind_short_circuit_law(container, function)[source]

Ensures that you cannot bind from the empty property.

Parameters:
  • container (SingleFailableN[TypeVar(_FirstType), TypeVar(_SecondType), TypeVar(_ThirdType)]) –

  • function (Callable[[TypeVar(_FirstType)], KindN[SingleFailableN, TypeVar(_NewFirstType), TypeVar(_SecondType), TypeVar(_ThirdType)]]) –

Return type:

None

static apply_short_circuit_law(container, function)[source]

Ensures that you cannot apply from the empty property.

Parameters:
  • container (SingleFailableN[TypeVar(_FirstType), TypeVar(_SecondType), TypeVar(_ThirdType)]) –

  • function (Callable[[TypeVar(_FirstType)], TypeVar(_NewFirstType)]) –

Return type:

None

class SingleFailableN[source]

Bases: FailableN[_FirstType, _SecondType, _ThirdType]

Base type for types that have just only one failed value.

Like Maybe types where the only failed value is Nothing.

_laws: ClassVar[Sequence[Law]] = (<returns.primitives.laws.Law2 object>, <returns.primitives.laws.Law2 object>, <returns.primitives.laws.Law2 object>)

Some classes and interfaces might have laws, some might not have any.

abstract property empty: SingleFailableN[_FirstType, _SecondType, _ThirdType]

This property represents the failed value. :param self: :type self: TypeVar(_SingleFailableType, bound= SingleFailableN)

Return type:

SingleFailableN[TypeVar(_FirstType), TypeVar(_SecondType), TypeVar(_ThirdType)]

SingleFailable2

Type alias for kinds with two types arguments.

alias of SingleFailableN[_FirstType, _SecondType, NoReturn]

SingleFailable3

Type alias for kinds with three type arguments.

alias of SingleFailableN[_FirstType, _SecondType, _ThirdType]

class _DiverseFailableLawSpec[source]

Bases: LawSpecDef

Diverse Failable laws.

We need to be sure that .map, .bind, .apply and .alt works correctly for both success and failure types.

static map_short_circuit_law(raw_value, container, function)[source]

Ensures that you cannot map a failure.

Parameters:
  • raw_value (TypeVar(_SecondType)) –

  • container (DiverseFailableN[TypeVar(_FirstType), TypeVar(_SecondType), TypeVar(_ThirdType)]) –

  • function (Callable[[TypeVar(_FirstType)], TypeVar(_NewFirstType)]) –

Return type:

None

static bind_short_circuit_law(raw_value, container, function)[source]

Ensures that you cannot bind a failure.

See: https://wiki.haskell.org/Typeclassopedia#MonadFail

Parameters:
  • raw_value (TypeVar(_SecondType)) –

  • container (DiverseFailableN[TypeVar(_FirstType), TypeVar(_SecondType), TypeVar(_ThirdType)]) –

  • function (Callable[[TypeVar(_FirstType)], KindN[DiverseFailableN, TypeVar(_NewFirstType), TypeVar(_SecondType), TypeVar(_ThirdType)]]) –

Return type:

None

static apply_short_circuit_law(raw_value, container, function)[source]

Ensures that you cannot apply a failure.

Parameters:
  • raw_value (TypeVar(_SecondType)) –

  • container (DiverseFailableN[TypeVar(_FirstType), TypeVar(_SecondType), TypeVar(_ThirdType)]) –

  • function (Callable[[TypeVar(_FirstType)], TypeVar(_NewFirstType)]) –

Return type:

None

static alt_short_circuit_law(raw_value, container, function)[source]

Ensures that you cannot alt a success.

Parameters:
  • raw_value (TypeVar(_SecondType)) –

  • container (DiverseFailableN[TypeVar(_FirstType), TypeVar(_SecondType), TypeVar(_ThirdType)]) –

  • function (Callable[[TypeVar(_SecondType)], TypeVar(_NewFirstType)]) –

Return type:

None

class DiverseFailableN[source]

Bases: FailableN[_FirstType, _SecondType, _ThirdType], SwappableN[_FirstType, _SecondType, _ThirdType], Lawful[DiverseFailableN[_FirstType, _SecondType, _ThirdType]]

Base type for types that have any failed value.

Like Result types.

_laws: ClassVar[Sequence[Law]] = (<returns.primitives.laws.Law3 object>, <returns.primitives.laws.Law3 object>, <returns.primitives.laws.Law3 object>, <returns.primitives.laws.Law3 object>)

Some classes and interfaces might have laws, some might not have any.

abstract classmethod from_failure(inner_value)[source]

Unit method to create new containers from any raw value.

Parameters:
  • cls (Type[TypeVar(_DiverseFailableType, bound= DiverseFailableN)]) –

  • inner_value (TypeVar(_UpdatedType)) –

Return type:

KindN[TypeVar(_DiverseFailableType, bound= DiverseFailableN), TypeVar(_FirstType), TypeVar(_UpdatedType), TypeVar(_ThirdType)]

DiverseFailable2

Type alias for kinds with two type arguments.

alias of DiverseFailableN[_FirstType, _SecondType, NoReturn]

DiverseFailable3

Type alias for kinds with three type arguments.

alias of DiverseFailableN[_FirstType, _SecondType, _ThirdType]

Maybe specific

classDiagram LawSpecDef <|-- _LawSpec Lawful <|-- MaybeLikeN MaybeLikeN <|-- MaybeBasedN SingleFailableN <|-- MaybeLikeN Equable <|-- MaybeBasedN Unwrappable <|-- MaybeBasedN
class _LawSpec[source]

Bases: LawSpecDef

Maybe laws.

We need to be sure that .map, .bind, .bind_optional, and .lash works correctly for both successful and failed types.

static map_short_circuit_law(container, function)[source]

Ensures that you cannot map from failures.

Parameters:
  • container (MaybeLikeN[TypeVar(_FirstType), TypeVar(_SecondType), TypeVar(_ThirdType)]) –

  • function (Callable[[TypeVar(_FirstType)], TypeVar(_NewType1)]) –

Return type:

None

static bind_short_circuit_law(container, function)[source]

Ensures that you cannot bind from failures.

Parameters:
  • container (MaybeLikeN[TypeVar(_FirstType), TypeVar(_SecondType), TypeVar(_ThirdType)]) –

  • function (Callable[[TypeVar(_FirstType)], KindN[MaybeLikeN, TypeVar(_NewType1), TypeVar(_SecondType), TypeVar(_ThirdType)]]) –

Return type:

None

static bind_optional_short_circuit_law(container, function)[source]

Ensures that you cannot bind from failures.

Parameters:
  • container (MaybeLikeN[TypeVar(_FirstType), TypeVar(_SecondType), TypeVar(_ThirdType)]) –

  • function (Callable[[TypeVar(_FirstType)], Optional[TypeVar(_NewType1)]]) –

Return type:

None

static lash_short_circuit_law(raw_value, container, function)[source]

Ensures that you cannot lash a success.

Parameters:
  • raw_value (TypeVar(_FirstType)) –

  • container (MaybeLikeN[TypeVar(_FirstType), TypeVar(_SecondType), TypeVar(_ThirdType)]) –

  • function (Callable[[TypeVar(_SecondType)], KindN[MaybeLikeN, TypeVar(_FirstType), TypeVar(_NewType1), TypeVar(_ThirdType)]]) –

Return type:

None

static unit_structure_law(container, function)[source]

Ensures None is treated specially.

Parameters:
  • container (MaybeLikeN[TypeVar(_FirstType), TypeVar(_SecondType), TypeVar(_ThirdType)]) –

  • function (Callable[[TypeVar(_FirstType)], None]) –

Return type:

None

class MaybeLikeN[source]

Bases: SingleFailableN[_FirstType, _SecondType, _ThirdType], Lawful[MaybeLikeN[_FirstType, _SecondType, _ThirdType]]

Type for values that do look like a Maybe.

For example, RequiresContextMaybe should be created from this interface. Cannot be unwrapped or compared.

_laws: ClassVar[Sequence[Law]] = (<returns.primitives.laws.Law2 object>, <returns.primitives.laws.Law2 object>, <returns.primitives.laws.Law2 object>, <returns.primitives.laws.Law3 object>, <returns.primitives.laws.Law2 object>)

Some classes and interfaces might have laws, some might not have any.

abstract bind_optional(function)[source]

Binds a function that returns Optional values.

Parameters:
  • self (TypeVar(_MaybeLikeType, bound= MaybeLikeN)) –

  • function (Callable[[TypeVar(_FirstType)], Optional[TypeVar(_UpdatedType)]]) –

Return type:

KindN[TypeVar(_MaybeLikeType, bound= MaybeLikeN), TypeVar(_UpdatedType), TypeVar(_SecondType), TypeVar(_ThirdType)]

abstract classmethod from_optional(inner_value)[source]

Unit method to create containers from Optional value.

Parameters:
  • cls (Type[TypeVar(_MaybeLikeType, bound= MaybeLikeN)]) –

  • inner_value (Optional[TypeVar(_ValueType)]) –

Return type:

KindN[TypeVar(_MaybeLikeType, bound= MaybeLikeN), TypeVar(_ValueType), TypeVar(_SecondType), TypeVar(_ThirdType)]

MaybeLike2

Type alias for kinds with two type arguments.

alias of MaybeLikeN[_FirstType, _SecondType, NoReturn]

MaybeLike3

Type alias for kinds with three type arguments.

alias of MaybeLikeN[_FirstType, _SecondType, _ThirdType]

class MaybeBasedN[source]

Bases: MaybeLikeN[_FirstType, _SecondType, _ThirdType], Unwrappable[_FirstType, None], Equable

Concrete interface for Maybe type.

Can be unwrapped and compared.

abstract or_else_call(function)[source]

Calls a function in case there nothing to unwrap.

Parameters:

function (Callable[[], TypeVar(_ValueType)]) –

Return type:

Union[TypeVar(_FirstType), TypeVar(_ValueType)]

MaybeBased2

Type alias for kinds with two type arguments.

alias of MaybeBasedN[_FirstType, _SecondType, NoReturn]

MaybeBased3

Type alias for kinds with three type arguments.

alias of MaybeBasedN[_FirstType, _SecondType, _ThirdType]

Result specific

classDiagram ResultLikeN <|-- UnwrappableResult Equable <|-- UnwrappableResult DiverseFailableN <|-- ResultLikeN UnwrappableResult <|-- ResultBasedN Unwrappable <|-- UnwrappableResult

An interface that represents a pure computation result.

For impure result see returns.interfaces.specific.ioresult.IOResultLikeN type.

class ResultLikeN[source]

Bases: DiverseFailableN[_FirstType, _SecondType, _ThirdType]

Base types for types that looks like Result but cannot be unwrapped.

Like RequiresContextResult or FutureResult.

abstract bind_result(function)[source]

Runs Result returning function over a container.

Parameters:
  • self (TypeVar(_ResultLikeType, bound= ResultLikeN)) –

  • function (Callable[[TypeVar(_FirstType)], Result[TypeVar(_UpdatedType), TypeVar(_SecondType)]]) –

Return type:

KindN[TypeVar(_ResultLikeType, bound= ResultLikeN), TypeVar(_UpdatedType), TypeVar(_SecondType), TypeVar(_ThirdType)]

abstract classmethod from_result(inner_value)[source]

Unit method to create new containers from any raw value.

Parameters:
  • cls (Type[TypeVar(_ResultLikeType, bound= ResultLikeN)]) –

  • inner_value (Result[TypeVar(_ValueType), TypeVar(_ErrorType)]) –

Return type:

KindN[TypeVar(_ResultLikeType, bound= ResultLikeN), TypeVar(_ValueType), TypeVar(_ErrorType), TypeVar(_ThirdType)]

ResultLike2

Type alias for kinds with two type arguments.

alias of ResultLikeN[_FirstType, _SecondType, NoReturn]

ResultLike3

Type alias for kinds with three type arguments.

alias of ResultLikeN[_FirstType, _SecondType, _ThirdType]

class UnwrappableResult[source]

Bases: ResultLikeN[_FirstType, _SecondType, _ThirdType], Unwrappable[_FirstUnwrappableType, _SecondUnwrappableType], Equable

Intermediate type with 5 type arguments that represents unwrappable result.

It is a raw type and should not be used directly. Use ResultBasedN and IOResultBasedN instead.

class ResultBasedN[source]

Bases: UnwrappableResult[_FirstType, _SecondType, _ThirdType, _FirstType, _SecondType]

Base type for real Result types.

Can be unwrapped.

ResultBased2

Type alias for kinds with two type arguments.

alias of ResultBasedN[_FirstType, _SecondType, NoReturn]

ResultBased3

Type alias for kinds with three type arguments.

alias of ResultBasedN[_FirstType, _SecondType, _ThirdType]

IO specific

classDiagram ContainerN <|-- IOLikeN Equable <|-- IOBasedN IOLikeN <|-- IOBasedN
class IOLikeN[source]

Bases: ContainerN[_FirstType, _SecondType, _ThirdType]

Represents interface for types that looks like fearless IO.

This type means that IO cannot fail. Like random numbers, date, etc. Don’t use this type for IO that can. Instead, use returns.interfaces.specific.ioresult.IOResultBasedN type.

abstract bind_io(function)[source]

Allows to apply a wrapped function over a container.

Parameters:
  • self (TypeVar(_IOLikeType, bound= IOLikeN)) –

  • function (Callable[[TypeVar(_FirstType)], IO[TypeVar(_UpdatedType)]]) –

Return type:

KindN[TypeVar(_IOLikeType, bound= IOLikeN), TypeVar(_UpdatedType), TypeVar(_SecondType), TypeVar(_ThirdType)]

abstract classmethod from_io(inner_value)[source]

Unit method to create new containers from successful IO.

Parameters:
  • cls (Type[TypeVar(_IOLikeType, bound= IOLikeN)]) –

  • inner_value (IO[TypeVar(_UpdatedType)]) –

Return type:

KindN[TypeVar(_IOLikeType, bound= IOLikeN), TypeVar(_UpdatedType), TypeVar(_SecondType), TypeVar(_ThirdType)]

IOLike1

Type alias for kinds with one type argument.

alias of IOLikeN[_FirstType, NoReturn, NoReturn]

IOLike2

Type alias for kinds with two type arguments.

alias of IOLikeN[_FirstType, _SecondType, NoReturn]

IOLike3

Type alias for kinds with three type arguments.

alias of IOLikeN[_FirstType, _SecondType, _ThirdType]

class IOBasedN[source]

Bases: IOLikeN[_FirstType, _SecondType, _ThirdType], Equable

Represents the base interface for types that do fearless IO.

This type means that IO cannot fail. Like random numbers, date, etc. Don’t use this type for IO that can. Instead, use returns.interfaces.specific.ioresult.IOResultBasedN type.

This interface also supports direct comparison of two values. While IOLikeN is different. It can be lazy and cannot be compared.

IOBased1

Type alias for kinds with one type argument.

alias of IOBasedN[_FirstType, NoReturn, NoReturn]

IOBased2

Type alias for kinds with two type arguments.

alias of IOBasedN[_FirstType, _SecondType, NoReturn]

IOBased3

Type alias for kinds with three type arguments.

alias of IOBasedN[_FirstType, _SecondType, _ThirdType]

IOResult specific

classDiagram IOLikeN <|-- IOResultLikeN ResultLikeN <|-- IOResultLikeN UnwrappableResult <|-- IOResultBasedN IOBasedN <|-- IOResultBasedN IOResultLikeN <|-- IOResultBasedN

An interface for types that do IO and can fail.

It is a base interface for both sync and async IO stacks.

class IOResultLikeN[source]

Bases: IOLikeN[_FirstType, _SecondType, _ThirdType], ResultLikeN[_FirstType, _SecondType, _ThirdType]

Base type for types that look like IOResult but cannot be unwrapped.

Like FutureResult or RequiresContextIOResult.

abstract bind_ioresult(function)[source]

Runs IOResult returning function over a container.

Parameters:
  • self (TypeVar(_IOResultLikeType, bound= IOResultLikeN)) –

  • function (Callable[[TypeVar(_FirstType)], IOResult[TypeVar(_UpdatedType), TypeVar(_SecondType)]]) –

Return type:

KindN[TypeVar(_IOResultLikeType, bound= IOResultLikeN), TypeVar(_UpdatedType), TypeVar(_SecondType), TypeVar(_ThirdType)]

abstract compose_result(function)[source]

Allows to compose the underlying Result with a function.

Parameters:
  • self (TypeVar(_IOResultLikeType, bound= IOResultLikeN)) –

  • function (Callable[[Result[TypeVar(_FirstType), TypeVar(_SecondType)]], KindN[TypeVar(_IOResultLikeType, bound= IOResultLikeN), TypeVar(_UpdatedType), TypeVar(_SecondType), TypeVar(_ThirdType)]]) –

Return type:

KindN[TypeVar(_IOResultLikeType, bound= IOResultLikeN), TypeVar(_UpdatedType), TypeVar(_SecondType), TypeVar(_ThirdType)]

abstract classmethod from_ioresult(inner_value)[source]

Unit method to create new containers from IOResult type.

Parameters:
  • cls (Type[TypeVar(_IOResultLikeType, bound= IOResultLikeN)]) –

  • inner_value (IOResult[TypeVar(_ValueType), TypeVar(_ErrorType)]) –

Return type:

KindN[TypeVar(_IOResultLikeType, bound= IOResultLikeN), TypeVar(_ValueType), TypeVar(_ErrorType), TypeVar(_ThirdType)]

abstract classmethod from_failed_io(inner_value)[source]

Unit method to create new containers from failed IO.

Parameters:
  • cls (Type[TypeVar(_IOResultLikeType, bound= IOResultLikeN)]) –

  • inner_value (IO[TypeVar(_ErrorType)]) –

Return type:

KindN[TypeVar(_IOResultLikeType, bound= IOResultLikeN), TypeVar(_FirstType), TypeVar(_ErrorType), TypeVar(_ThirdType)]

IOResultLike2

Type alias for kinds with two type arguments.

alias of IOResultLikeN[_FirstType, _SecondType, NoReturn]

IOResultLike3

Type alias for kinds with three type arguments.

alias of IOResultLikeN[_FirstType, _SecondType, _ThirdType]

class IOResultBasedN[source]

Bases: IOResultLikeN[_FirstType, _SecondType, _ThirdType], IOBasedN[_FirstType, _SecondType, _ThirdType], UnwrappableResult[_FirstType, _SecondType, _ThirdType, IO[_FirstType], IO[_SecondType]]

Base type for real IOResult types.

Can be unwrapped.

IOResultBased2

Type alias for kinds with two type arguments.

alias of IOResultBasedN[_FirstType, _SecondType, NoReturn]

IOResultBased3

Type alias for kinds with three type arguments.

alias of IOResultBasedN[_FirstType, _SecondType, _ThirdType]

Future specific

classDiagram Generic <|-- AwaitableFutureN IOLikeN <|-- FutureLikeN AwaitableFutureN <|-- FutureBasedN FutureLikeN <|-- FutureBasedN

Represents the base interfaces for types that do fearless async operations.

This type means that Future cannot fail. Don’t use this type for async that can. Instead, use returns.interfaces.specific.future_result.FutureResultBasedN type.

class FutureLikeN[source]

Bases: IOLikeN[_FirstType, _SecondType, _ThirdType]

Base type for ones that does look like Future.

But at the time this is not a real Future and cannot be awaited.

abstract bind_future(function)[source]

Allows to bind Future returning function over a container.

Parameters:
  • self (TypeVar(_FutureLikeType, bound= FutureLikeN)) –

  • function (Callable[[TypeVar(_FirstType)], Future[TypeVar(_UpdatedType)]]) –

Return type:

KindN[TypeVar(_FutureLikeType, bound= FutureLikeN), TypeVar(_UpdatedType), TypeVar(_SecondType), TypeVar(_ThirdType)]

abstract bind_async_future(function)[source]

Allows to bind async Future returning function over container.

Parameters:
  • self (TypeVar(_FutureLikeType, bound= FutureLikeN)) –

  • function (Callable[[TypeVar(_FirstType)], Awaitable[Future[TypeVar(_UpdatedType)]]]) –

Return type:

KindN[TypeVar(_FutureLikeType, bound= FutureLikeN), TypeVar(_UpdatedType), TypeVar(_SecondType), TypeVar(_ThirdType)]

abstract bind_async(function)[source]

Binds async function returning the same type of container.

Parameters:
  • self (TypeVar(_FutureLikeType, bound= FutureLikeN)) –

  • function (Callable[[TypeVar(_FirstType)], Awaitable[KindN[TypeVar(_FutureLikeType, bound= FutureLikeN), TypeVar(_UpdatedType), TypeVar(_SecondType), TypeVar(_ThirdType)]]]) –

Return type:

KindN[TypeVar(_FutureLikeType, bound= FutureLikeN), TypeVar(_UpdatedType), TypeVar(_SecondType), TypeVar(_ThirdType)]

abstract bind_awaitable(function)[source]

Allows to bind async function over container.

Parameters:
  • self (TypeVar(_FutureLikeType, bound= FutureLikeN)) –

  • function (Callable[[TypeVar(_FirstType)], Awaitable[TypeVar(_UpdatedType)]]) –

Return type:

KindN[TypeVar(_FutureLikeType, bound= FutureLikeN), TypeVar(_UpdatedType), TypeVar(_SecondType), TypeVar(_ThirdType)]

abstract classmethod from_future(inner_value)[source]

Unit method to create new containers from successful Future.

Parameters:
  • cls (Type[TypeVar(_FutureLikeType, bound= FutureLikeN)]) –

  • inner_value (Future[TypeVar(_UpdatedType)]) –

Return type:

KindN[TypeVar(_FutureLikeType, bound= FutureLikeN), TypeVar(_UpdatedType), TypeVar(_SecondType), TypeVar(_ThirdType)]

FutureLike1

Type alias for kinds with one type argument.

alias of FutureLikeN[_FirstType, NoReturn, NoReturn]

FutureLike2

Type alias for kinds with two type arguments.

alias of FutureLikeN[_FirstType, _SecondType, NoReturn]

FutureLike3

Type alias for kinds with three type arguments.

alias of FutureLikeN[_FirstType, _SecondType, _ThirdType]

class AwaitableFutureN[source]

Bases: Generic[_FirstType, _SecondType, _ThirdType]

Type that provides the required API for Future to be async.

Should not be used directly. Use FutureBasedN instead.

abstract async awaitable()[source]

Underling logic under await expression.

Parameters:

self (TypeVar(_AsyncFutureType, bound= AwaitableFutureN)) –

Return type:

IOLikeN[TypeVar(_FirstType), TypeVar(_SecondType), TypeVar(_ThirdType)]

AsyncFuture1

Type alias for kinds with one type argument.

alias of AwaitableFutureN[_FirstType, NoReturn, NoReturn]

AsyncFuture2

Type alias for kinds with two type arguments.

alias of AwaitableFutureN[_FirstType, _SecondType, NoReturn]

AsyncFuture3

Type alias for kinds with three type arguments.

alias of AwaitableFutureN[_FirstType, _SecondType, _ThirdType]

class FutureBasedN[source]

Bases: FutureLikeN[_FirstType, _SecondType, _ThirdType], AwaitableFutureN[_FirstType, _SecondType, _ThirdType]

Base type for real Future objects.

They can be awaited.

FutureBased1

Type alias for kinds with one type argument.

alias of FutureBasedN[_FirstType, NoReturn, NoReturn]

FutureBased2

Type alias for kinds with two type arguments.

alias of FutureBasedN[_FirstType, _SecondType, NoReturn]

FutureBased3

Type alias for kinds with three type arguments.

alias of FutureBasedN[_FirstType, _SecondType, _ThirdType]

FutureResult specific

classDiagram FutureLikeN <|-- FutureResultLikeN FutureResultLikeN <|-- FutureResultBasedN FutureBasedN <|-- FutureResultBasedN IOResultLikeN <|-- FutureResultLikeN

Represents the base interfaces for types that do fear-some async operations.

This type means that FutureResult can (and will!) fail with exceptions.

Use this type to mark that this specific async opetaion can fail.

class FutureResultLikeN[source]

Bases: FutureLikeN[_FirstType, _SecondType, _ThirdType], IOResultLikeN[_FirstType, _SecondType, _ThirdType]

Base type for ones that does look like FutureResult.

But at the time this is not a real Future and cannot be awaited. It is also cannot be unwrapped, because it is not a real IOResult.

abstract bind_future_result(function)[source]

Allows to bind FutureResult functions over a container.

Parameters:
  • self (TypeVar(_FutureResultLikeType, bound= FutureResultLikeN)) –

  • function (Callable[[TypeVar(_FirstType)], FutureResult[TypeVar(_UpdatedType), TypeVar(_SecondType)]]) –

Return type:

KindN[TypeVar(_FutureResultLikeType, bound= FutureResultLikeN), TypeVar(_UpdatedType), TypeVar(_SecondType), TypeVar(_ThirdType)]

abstract bind_async_future_result(function)[source]

Allows to bind async FutureResult functions over container.

Parameters:
  • self (TypeVar(_FutureResultLikeType, bound= FutureResultLikeN)) –

  • function (Callable[[TypeVar(_FirstType)], Awaitable[FutureResult[TypeVar(_UpdatedType), TypeVar(_SecondType)]]]) –

Return type:

KindN[TypeVar(_FutureResultLikeType, bound= FutureResultLikeN), TypeVar(_UpdatedType), TypeVar(_SecondType), TypeVar(_ThirdType)]

abstract classmethod from_failed_future(inner_value)[source]

Creates new container from a failed Future.

Parameters:
  • cls (Type[TypeVar(_FutureResultLikeType, bound= FutureResultLikeN)]) –

  • inner_value (Future[TypeVar(_ErrorType)]) –

Return type:

KindN[TypeVar(_FutureResultLikeType, bound= FutureResultLikeN), TypeVar(_FirstType), TypeVar(_ErrorType), TypeVar(_ThirdType)]

classmethod from_future_result(inner_value)[source]

Creates container from FutureResult instance.

Parameters:
  • cls (Type[TypeVar(_FutureResultLikeType, bound= FutureResultLikeN)]) –

  • inner_value (FutureResult[TypeVar(_ValueType), TypeVar(_ErrorType)]) –

Return type:

KindN[TypeVar(_FutureResultLikeType, bound= FutureResultLikeN), TypeVar(_ValueType), TypeVar(_ErrorType), TypeVar(_ThirdType)]

FutureResultLike2

Type alias for kinds with two type arguments.

alias of FutureResultLikeN[_FirstType, _SecondType, NoReturn]

FutureResultLike3

Type alias for kinds with three type arguments.

alias of FutureResultLikeN[_FirstType, _SecondType, _ThirdType]

class FutureResultBasedN[source]

Bases: FutureBasedN[_FirstType, _SecondType, _ThirdType], FutureResultLikeN[_FirstType, _SecondType, _ThirdType]

Base type for real FutureResult objects.

They can be awaited. Still cannot be unwrapped.

FutureResultBased2

Type alias for kinds with two type arguments.

alias of FutureResultBasedN[_FirstType, _SecondType, NoReturn]

FutureResultBased3

Type alias for kinds with three type arguments.

alias of FutureResultBasedN[_FirstType, _SecondType, _ThirdType]

Reader specific

classDiagram LawSpecDef <|-- _LawSpec Lawful <|-- ReaderBased2 ContainerN <|-- ReaderLike2 ReaderLike2 <|-- CallableReader2 ContainerN <|-- ReaderLike3 ReaderLike3 <|-- CallableReader3 Contextable <|-- CallableReader2 Contextable <|-- CallableReader3 Generic <|-- Contextable CallableReader2 <|-- ReaderBased2

This module is special.

Reader does not produce ReaderLikeN interface as other containers.

Because Reader can be used with two or three type arguments: - RequiresContext[value, env] - RequiresContextResult[value, error, env]

Because the second type argument changes its meaning based on the used KindN instance, we need to have two separate interfaces for two separate use-cases: - ReaderLike2 is used for types where the second type argument is env - ReaderLike3 is used for types where the third type argument is env

We also have two methods and two poinfree helpers for bind_context composition: one for each interface.

Furthermore, Reader cannot have ReaderLike1 type, because we need both value and env types at all cases.

class Contextable[source]

Bases: Generic[_ValueType, _EnvType]

Special type we use as a base one for all callble Reader instances.

It only has a single method. And is a base type for every single one of them.

But, each Reader defines the return type differently. For example:

  • Reader has just _ReturnType

  • ReaderResult has Result[_FirstType, _SecondType]

  • ReaderIOResult has IOResult[_FirstType, _SecondType]

And so on.

class ReaderLike2[source]

Bases: ContainerN[_FirstType, _SecondType, NoReturn]

Reader interface for Kind2 based types.

It has two type arguments and treats the second type argument as env type.

abstract property no_args: NoDeps

Is required to call Reader with no explicit arguments. :param self: :type self: TypeVar(_ReaderLike2Type, bound= ReaderLike2)

Return type:

Any

abstract bind_context(function)[source]

Allows to apply a wrapped function over a Reader container.

Parameters:
  • self (TypeVar(_ReaderLike2Type, bound= ReaderLike2)) –

  • function (Callable[[TypeVar(_FirstType)], RequiresContext[TypeVar(_UpdatedType), TypeVar(_SecondType)]]) –

Return type:

KindN[TypeVar(_ReaderLike2Type, bound= ReaderLike2), TypeVar(_UpdatedType), TypeVar(_SecondType), Any]

abstract modify_env(function)[source]

Transforms the environment before calling the container.

Parameters:
  • self (TypeVar(_ReaderLike2Type, bound= ReaderLike2)) –

  • function (Callable[[TypeVar(_UpdatedType)], TypeVar(_SecondType)]) –

Return type:

KindN[TypeVar(_ReaderLike2Type, bound= ReaderLike2), TypeVar(_FirstType), TypeVar(_UpdatedType), Any]

abstract classmethod ask()[source]

Returns the dependencies inside the container.

Parameters:

cls (Type[TypeVar(_ReaderLike2Type, bound= ReaderLike2)]) –

Return type:

KindN[TypeVar(_ReaderLike2Type, bound= ReaderLike2), TypeVar(_SecondType), TypeVar(_SecondType), Any]

abstract classmethod from_context(inner_value)[source]

Unit method to create new containers from successful Reader.

Parameters:
  • cls (Type[TypeVar(_ReaderLike2Type, bound= ReaderLike2)]) –

  • inner_value (RequiresContext[TypeVar(_ValueType), TypeVar(_EnvType)]) –

Return type:

KindN[TypeVar(_ReaderLike2Type, bound= ReaderLike2), TypeVar(_ValueType), TypeVar(_EnvType), Any]

class CallableReader2[source]

Bases: ReaderLike2[_FirstType, _SecondType], Contextable[_ValueType, _EnvType]

Intermediate interface for ReaderLike2 + __call__ method.

Has 4 type variables to type Reader and __call__ independently. Since, we don’t have any other fancy ways of doing it.

Should not be used directly other than defining your own Reader interfaces.

class ReaderLike3[source]

Bases: ContainerN[_FirstType, _SecondType, _ThirdType]

Reader interface for Kind3 based types.

It has three type arguments and treats the third type argument as env type. The second type argument is not used here.

abstract property no_args: Any

Is required to call Reader with no explicit arguments. :param self: :type self: TypeVar(_ReaderLike3Type, bound= ReaderLike3)

Return type:

Any

abstract bind_context(function)[source]

Allows to apply a wrapped function over a Reader container.

Parameters:
  • self (TypeVar(_ReaderLike3Type, bound= ReaderLike3)) –

  • function (Callable[[TypeVar(_FirstType)], RequiresContext[TypeVar(_UpdatedType), TypeVar(_ThirdType)]]) –

Return type:

KindN[TypeVar(_ReaderLike3Type, bound= ReaderLike3), TypeVar(_UpdatedType), TypeVar(_SecondType), TypeVar(_ThirdType)]

abstract modify_env(function)[source]

Transforms the environment before calling the container.

Parameters:
  • self (TypeVar(_ReaderLike3Type, bound= ReaderLike3)) –

  • function (Callable[[TypeVar(_UpdatedType)], TypeVar(_ThirdType)]) –

Return type:

KindN[TypeVar(_ReaderLike3Type, bound= ReaderLike3), TypeVar(_FirstType), TypeVar(_SecondType), TypeVar(_UpdatedType)]

abstract classmethod ask()[source]

Returns the dependencies inside the container.

Parameters:

cls (Type[TypeVar(_ReaderLike3Type, bound= ReaderLike3)]) –

Return type:

KindN[TypeVar(_ReaderLike3Type, bound= ReaderLike3), TypeVar(_ThirdType), TypeVar(_SecondType), TypeVar(_ThirdType)]

abstract classmethod from_context(inner_value)[source]

Unit method to create new containers from successful Reader.

Parameters:
  • cls (Type[TypeVar(_ReaderLike3Type, bound= ReaderLike3)]) –

  • inner_value (RequiresContext[TypeVar(_ValueType), TypeVar(_EnvType)]) –

Return type:

KindN[TypeVar(_ReaderLike3Type, bound= ReaderLike3), TypeVar(_ValueType), TypeVar(_SecondType), TypeVar(_EnvType)]

class CallableReader3[source]

Bases: ReaderLike3[_FirstType, _SecondType, _ThirdType], Contextable[_ValueType, _EnvType]

Intermediate interface for ReaderLike3 + __call__ method.

Has 5 type variables to type Reader and __call__ independently. Since, we don’t have any other fancy ways of doing it.

Should not be used directly other than defining your own Reader interfaces.

class _LawSpec[source]

Bases: LawSpecDef

Concrete laws for ReaderBased2.

See: https://github.com/haskell/mtl/pull/61/files

static purity_law(container, env)[source]

Calling a Reader twice has the same result with the same env.

Parameters:
  • container (ReaderBased2[TypeVar(_FirstType), TypeVar(_SecondType)]) –

  • env (TypeVar(_SecondType)) –

Return type:

None

static asking_law(container, env)[source]

Asking for an env, always returns the env.

Parameters:
  • container (ReaderBased2[TypeVar(_FirstType), TypeVar(_SecondType)]) –

  • env (TypeVar(_SecondType)) –

Return type:

None

class ReaderBased2[source]

Bases: CallableReader2[_FirstType, _SecondType, _FirstType, _SecondType], Lawful[ReaderBased2[_FirstType, _SecondType]]

This interface is very specific to our Reader type.

The only thing that differs from ReaderLike2 is that we know the specific types for its __call__ method.

_laws: ClassVar[Sequence[Law]] = (<returns.primitives.laws.Law2 object>, <returns.primitives.laws.Law2 object>)

Some classes and interfaces might have laws, some might not have any.

ReaderResult specific

classDiagram LawSpecDef <|-- _LawSpec CallableReader3 <|-- ReaderResultBasedN ResultLikeN <|-- ReaderResultLikeN Lawful <|-- ReaderResultBasedN ReaderLike3 <|-- ReaderResultLikeN ReaderResultLikeN <|-- ReaderResultBasedN
class ReaderResultLikeN[source]

Bases: ReaderLike3[_FirstType, _SecondType, _ThirdType], ResultLikeN[_FirstType, _SecondType, _ThirdType]

Base interface for all types that do look like ReaderResult instance.

Cannot be called.

abstract bind_context_result(function)[source]

Binds a ReaderResult returning function over a container.

Parameters:
  • self (TypeVar(_ReaderResultLikeType, bound= ReaderResultLikeN)) –

  • function (Callable[[TypeVar(_FirstType)], RequiresContextResult[TypeVar(_UpdatedType), TypeVar(_SecondType), TypeVar(_ThirdType)]]) –

Return type:

KindN[TypeVar(_ReaderResultLikeType, bound= ReaderResultLikeN), TypeVar(_UpdatedType), TypeVar(_SecondType), TypeVar(_ThirdType)]

abstract classmethod from_failed_context(inner_value)[source]

Unit method to create new containers from failed Reader.

Parameters:
  • cls (Type[TypeVar(_ReaderResultLikeType, bound= ReaderResultLikeN)]) –

  • inner_value (RequiresContext[TypeVar(_ErrorType), TypeVar(_EnvType)]) –

Return type:

KindN[TypeVar(_ReaderResultLikeType, bound= ReaderResultLikeN), TypeVar(_FirstType), TypeVar(_ErrorType), TypeVar(_EnvType)]

abstract classmethod from_result_context(inner_value)[source]

Unit method to create new containers from ReaderResult.

Parameters:
  • cls (Type[TypeVar(_ReaderResultLikeType, bound= ReaderResultLikeN)]) –

  • inner_value (RequiresContextResult[TypeVar(_ValueType), TypeVar(_ErrorType), TypeVar(_EnvType)]) –

Return type:

KindN[TypeVar(_ReaderResultLikeType, bound= ReaderResultLikeN), TypeVar(_ValueType), TypeVar(_ErrorType), TypeVar(_EnvType)]

ReaderResultLike3

Type alias for kinds with three type arguments.

alias of ReaderResultLikeN[_FirstType, _SecondType, _ThirdType]

class _LawSpec[source]

Bases: LawSpecDef

Concrete laws for ReaderResulBasedN.

See: https://github.com/haskell/mtl/pull/61/files

static purity_law(container, env)[source]

Calling a Reader twice has the same result with the same env.

Parameters:
  • container (ReaderResultBasedN[TypeVar(_FirstType), TypeVar(_SecondType), TypeVar(_ThirdType)]) –

  • env (TypeVar(_ThirdType)) –

Return type:

None

static asking_law(container, env)[source]

Asking for an env, always returns the env.

Parameters:
  • container (ReaderResultBasedN[TypeVar(_FirstType), TypeVar(_SecondType), TypeVar(_ThirdType)]) –

  • env (TypeVar(_ThirdType)) –

Return type:

None

class ReaderResultBasedN[source]

Bases: ReaderResultLikeN[_FirstType, _SecondType, _ThirdType], CallableReader3[_FirstType, _SecondType, _ThirdType, Result[_FirstType, _SecondType], _ThirdType], Lawful[ReaderResultBasedN[_FirstType, _SecondType, _ThirdType]]

This interface is very specific to our ReaderResult type.

The only thing that differs from ReaderResultLikeN is that we know the specific types for its __call__ method.

In this case the return type of __call__ is Result.

_laws: ClassVar[Sequence[Law]] = (<returns.primitives.laws.Law2 object>, <returns.primitives.laws.Law2 object>)

Some classes and interfaces might have laws, some might not have any.

ReaderResultBased3

Type alias for kinds with three type arguments.

alias of ReaderResultBasedN[_FirstType, _SecondType, _ThirdType]

ReaderIOResult specific

classDiagram LawSpecDef <|-- _LawSpec CallableReader3 <|-- ReaderIOResultBasedN Lawful <|-- ReaderIOResultBasedN ReaderIOResultLikeN <|-- ReaderIOResultBasedN IOResultLikeN <|-- ReaderIOResultLikeN ReaderResultLikeN <|-- ReaderIOResultLikeN
class ReaderIOResultLikeN[source]

Bases: ReaderResultLikeN[_FirstType, _SecondType, _ThirdType], IOResultLikeN[_FirstType, _SecondType, _ThirdType]

Base interface for all types that do look like ReaderIOResult instance.

Cannot be called.

abstract bind_context_ioresult(function)[source]

Binds a ReaderIOResult returning function over a container.

Parameters:
  • self (TypeVar(_ReaderIOResultLikeType, bound= ReaderIOResultLikeN)) –

  • function (Callable[[TypeVar(_FirstType)], RequiresContextIOResult[TypeVar(_UpdatedType), TypeVar(_SecondType), TypeVar(_ThirdType)]]) –

Return type:

KindN[TypeVar(_ReaderIOResultLikeType, bound= ReaderIOResultLikeN), TypeVar(_UpdatedType), TypeVar(_SecondType), TypeVar(_ThirdType)]

abstract classmethod from_ioresult_context(inner_value)[source]

Unit method to create new containers from ReaderIOResult.

Parameters:
  • cls (Type[TypeVar(_ReaderIOResultLikeType, bound= ReaderIOResultLikeN)]) –

  • inner_value (RequiresContextIOResult[TypeVar(_ValueType), TypeVar(_ErrorType), TypeVar(_EnvType)]) –

Return type:

KindN[TypeVar(_ReaderIOResultLikeType, bound= ReaderIOResultLikeN), TypeVar(_ValueType), TypeVar(_ErrorType), TypeVar(_EnvType)]

ReaderIOResultLike3

Type alias for kinds with three type arguments.

alias of ReaderIOResultLikeN[_FirstType, _SecondType, _ThirdType]

class _LawSpec[source]

Bases: LawSpecDef

Concrete laws for ReaderIOResultBasedN.

See: https://github.com/haskell/mtl/pull/61/files

static asking_law(container, env)[source]

Asking for an env, always returns the env.

Parameters:
  • container (ReaderIOResultBasedN[TypeVar(_FirstType), TypeVar(_SecondType), TypeVar(_ThirdType)]) –

  • env (TypeVar(_ThirdType)) –

Return type:

None

class ReaderIOResultBasedN[source]

Bases: ReaderIOResultLikeN[_FirstType, _SecondType, _ThirdType], CallableReader3[_FirstType, _SecondType, _ThirdType, IOResult[_FirstType, _SecondType], _ThirdType], Lawful[ReaderIOResultBasedN[_FirstType, _SecondType, _ThirdType]]

This interface is very specific to our ReaderIOResult type.

The only thing that differs from ReaderIOResultLikeN is that we know the specific types for its __call__ method.

In this case the return type of __call__ is IOResult.

_laws: ClassVar[Sequence[Law]] = (<returns.primitives.laws.Law2 object>,)

Some classes and interfaces might have laws, some might not have any.

ReaderIOResultBased3

Type alias for kinds with three type arguments.

alias of ReaderIOResultBasedN[_FirstType, _SecondType, _ThirdType]

ReaderFutureResult specific

classDiagram LawSpecDef <|-- _LawSpec Lawful <|-- ReaderFutureResultBasedN ReaderFutureResultLikeN <|-- ReaderFutureResultBasedN ReaderIOResultLikeN <|-- ReaderFutureResultLikeN CallableReader3 <|-- ReaderFutureResultBasedN FutureResultLikeN <|-- ReaderFutureResultLikeN
class ReaderFutureResultLikeN[source]

Bases: ReaderIOResultLikeN[_FirstType, _SecondType, _ThirdType], FutureResultLikeN[_FirstType, _SecondType, _ThirdType]

Interface for all types that do look like ReaderFutureResult instance.

Cannot be called.

abstract bind_context_future_result(function)[source]

Bind a ReaderFutureResult returning function over a container.

Parameters:
  • self (TypeVar(_ReaderFutureResultLikeType, bound= ReaderFutureResultLikeN)) –

  • function (Callable[[TypeVar(_FirstType)], RequiresContextFutureResult[TypeVar(_UpdatedType), TypeVar(_SecondType), TypeVar(_ThirdType)]]) –

Return type:

KindN[TypeVar(_ReaderFutureResultLikeType, bound= ReaderFutureResultLikeN), TypeVar(_UpdatedType), TypeVar(_SecondType), TypeVar(_ThirdType)]

abstract bind_async_context_future_result(function)[source]

Bind async ReaderFutureResult function.

Parameters:
  • self (TypeVar(_ReaderFutureResultLikeType, bound= ReaderFutureResultLikeN)) –

  • function (Callable[[TypeVar(_FirstType)], Awaitable[RequiresContextFutureResult[TypeVar(_UpdatedType), TypeVar(_SecondType), TypeVar(_ThirdType)]]]) –

Return type:

KindN[TypeVar(_ReaderFutureResultLikeType, bound= ReaderFutureResultLikeN), TypeVar(_UpdatedType), TypeVar(_SecondType), TypeVar(_ThirdType)]

abstract classmethod from_future_result_context(inner_value)[source]

Unit method to create new containers from ReaderFutureResult.

Parameters:
  • cls (Type[TypeVar(_ReaderFutureResultLikeType, bound= ReaderFutureResultLikeN)]) –

  • inner_value (RequiresContextFutureResult[TypeVar(_ValueType), TypeVar(_ErrorType), TypeVar(_EnvType)]) –

Return type:

KindN[TypeVar(_ReaderFutureResultLikeType, bound= ReaderFutureResultLikeN), TypeVar(_ValueType), TypeVar(_ErrorType), TypeVar(_EnvType)]

ReaderFutureResultLike3

Type alias for kinds with three type arguments.

alias of ReaderFutureResultLikeN[_FirstType, _SecondType, _ThirdType]

class _LawSpec[source]

Bases: LawSpecDef

Concrete laws for ReaderFutureResultBasedN.

See: https://github.com/haskell/mtl/pull/61/files

static asking_law(container, env)[source]

Asking for an env, always returns the env.

Parameters:
  • container (ReaderFutureResultBasedN[TypeVar(_FirstType), TypeVar(_SecondType), TypeVar(_ThirdType)]) –

  • env (TypeVar(_ThirdType)) –

Return type:

None

class ReaderFutureResultBasedN[source]

Bases: ReaderFutureResultLikeN[_FirstType, _SecondType, _ThirdType], CallableReader3[_FirstType, _SecondType, _ThirdType, FutureResult[_FirstType, _SecondType], _ThirdType], Lawful[ReaderFutureResultBasedN[_FirstType, _SecondType, _ThirdType]]

This interface is very specific to our ReaderFutureResult type.

The only thing that differs from ReaderFutureResultLikeN is that we know the specific types for its __call__ method.

In this case the return type of __call__ is FutureResult.

_laws: ClassVar[Sequence[Law]] = (<returns.primitives.laws.Law2 object>,)

Some classes and interfaces might have laws, some might not have any.

ReaderFutureResultBased3

Type alias for kinds with three type arguments.

alias of ReaderFutureResultBasedN[_FirstType, _SecondType, _ThirdType]