Interfaces¶

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

These interfaces are designed:

To be subclassed
To provide abstract methods to implement in your own types
To enforce correctness on final types
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]

Note

Useful links before you start here:

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.

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)

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.

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)

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)),
... )

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),
... )

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.

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)

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)

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:

Let’s review it one by one.

Equable¶

classDiagram LawSpecDef <|-- _LawSpec Lawful <|-- Equable

final 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

final 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.

See also

https://en.wikipedia.org/wiki/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

final 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.

See also

_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:: 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

final 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.

See also

https://typelevel.org/cats/typeclasses/bifunctor.html

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 BiMappableN <|-- SwappableN LawSpecDef <|-- _LawSpec Lawful <|-- SwappableN

final class _LawSpec[source]¶

Bases: LawSpecDef

Laws for SwappableN type.

static double_swap_law(container)[source]¶

Swapping 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 ApplicativeN <|-- ContainerN BindableN <|-- ContainerN LawSpecDef <|-- _LawSpec Lawful <|-- ContainerN

final 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.

See also

https://bit.ly/2CTEVov

_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¶

final 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]

final 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)

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]

final 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:: 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¶

final 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:: 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¶

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:: 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:: 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¶

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

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:: 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 FutureBasedN <|-- FutureResultBasedN FutureLikeN <|-- FutureResultLikeN FutureResultLikeN <|-- 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:: 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:: 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¶

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.

See also

https://github.com/dry-python/returns/issues/485

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)

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.

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:: 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)

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.

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:: 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.

final 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¶

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:: 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:: 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]

final 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¶

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:: 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]

final 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¶

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:: 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]

final 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]

← Higher Kinded Types Maybe →

Interfaces¶

General information¶

Naming convention¶

Laws¶

Mappable¶

Laws¶

Bindable¶

Applicative¶

Laws¶

Container¶

Laws¶

More!¶

Specific interfaces¶

FAQ¶

Why do you have general and specific interfaces?¶

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

What’s the difference between MappableN and BindableN?¶

What is the difference between ResultLikeN and ResultBasedN?¶

API Reference¶

Overview¶

Equable¶

Mappable¶

Bindable¶

Applicative¶

Altable¶

BiMappable¶

Swappable¶

Lashable¶

Unwrappable¶

Container¶

Failable¶

Maybe specific¶

Result specific¶

IO specific¶

IOResult specific¶

Future specific¶

FutureResult specific¶

Reader specific¶

ReaderResult specific¶

ReaderIOResult specific¶

ReaderFutureResult specific¶

What’s the difference between `MappableN` and `BindableN`?¶