typeapi 1.0.1

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typeapi

Compatibility: Python 3.6+

The typeapi package provides an object-oriented interface for introspecting type hints from the typing and typing_extensions module at runtime. Currently, only a subset of the different kinds of type hints are supported, namely through the following representations:

Concrete type	Description
ClassTypeHint	For any normal or generic type as well as typing.Any. Provides access to the underlying type, the type arguments and parameters, if any.
UnionTypeHint	Represents Union type hint and gives access to the union members.
LiteralTypeHint	Represents a Literal type hint and gives access to the literal values.
AnnotatedTypeHint	Represents an Annotated type hint and gives access to the annotated type as well as the metadata.
TypeVarTypeHint	Represents a TypeVar type hint and gives an interface to access the variable's metadata (such as constarints, variance, ...).
ForwardRefTypeHint	Represents a forward reference.

The main entry point to wrapping a low-level type hint is the TypeHint() constructor.

Examples

Inspect a List[int] type hint:

# cat <<EOF | python -
from typeapi import ClassTypeHint, TypeHint
from typing import List

hint = TypeHint(List[int])
assert isinstance(hint, ClassTypeHint)
assert hint.type is list

item_hint = hint[0]
assert isinstance(item_hint, ClassTypeHint)
assert item_hint.type is int

Retrieve the metadata from an Annotated[...] type hint:

# cat <<EOF | python -
from typeapi import AnnotatedTypeHint, ClassTypeHint, TypeHint
from typing_extensions import Annotated

hint = TypeHint(Annotated[int, 42])
assert isinstance(hint, AnnotatedTypeHint)
assert hint.type is int
assert hint.metadata == (42,)

sub_hint = hint[0]
assert isinstance(sub_hint, ClassTypeHint)
assert sub_hint.type is int

Parameterize one type hint with the parameterization of a generic alias:

# cat <<EOF | python -
from dataclasses import dataclass
from typeapi import ClassTypeHint, TypeHint
from typing import Generic, TypeVar
from typing_extensions import Annotated

T = TypeVar("T")

@dataclass
class MyGeneric(Generic[T]):
  value: T

hint = TypeHint(MyGeneric[int])
assert isinstance(hint, ClassTypeHint)
assert hint.get_parameter_map() == {T: int}

member_hint = TypeHint(T).parameterize(hint.get_parameter_map())
assert isinstance(member_hint, ClassTypeHint)
assert member_hint.type is int

Evaluate forward references:

# cat <<EOF | python -
from typeapi import ClassTypeHint, ForwardRefTypeHint, TypeHint
from typing import List

MyVector = List["MyType"]

class MyType:
  pass

hint = TypeHint(MyVector)
assert isinstance(hint, ClassTypeHint)
assert hint.type is list

item_hint = hint[0]
assert isinstance(item_hint, ForwardRefTypeHint)
assert item_hint.expr == "MyType"

hint = hint.evaluate(globals())
item_hint = hint[1]
assert isinstance(item_hint, ClassTypeHint)
assert item_hint.type is MyType

Planned work

• Support more features of the typing system (e.g. ClassVar, ParamSpec, ...)
• Support evaluating forward references that utilize newer Python language features (such as built-in type subscripts and type union syntax).
  • Subscript support could be achieved by mocking the built-in types during the evaluation of the expression.
  • Type unions could be achieved by rewriting the expression AST before evaluating and mocking every value in the expression.