Unpacking Python's Type Annotations -

i'm trying generate javascript based on type annotations have provided in on python functions using signature() function in inspect module.

this part works expect when type simple builtin class:

import inspect  def my_function() -> dict:     pass  signature = inspect.signature(my_function) signature.return_annotation dict  # true 

though i'm not sure how unwrap , inspect more complex annotations e.g:

from typing import list import inspect  def my_function() -> list[int]:     pass  signature = inspect.signature(my_function) signature.return_annotation list[int]  # false 

again similar problem forward referencing custom class:

def my_function() -> list['user']:     pass ... signature.return_annotation  # typing.list[_forwardref('user')] 

what i'm looking out - can branch appropriately while generating javascript:

type = signature.return_annotation... # list member_type = signature.return_annotation... # int / 'user' 

thanks.

list not map of types genericmeta, despite syntax. each access generates new instance:

>>> [ id(list[str]) in range(3) ] [33105112, 33106872, 33046936] 

this means list[int] not list[int]. compare 2 instances, have multiple options:

• use ==, i.e., signature.return_annotation == list[int].

• store instance of type in global variable , check against that, i.e.,

  a = list[int] def foo() -> a:     pass inspect.signature(foo).return_annotation 

• use issubclass. typing module defines that. note might more you'd like, make sure read _typealias documentation if use this.

• check against list , read contents yourself. though property internal, unlikely implementation change soon: list[int].__args__[0] contains type argument starting python 3.5.2, , in earlier versions, list[int].__parameters__[0].

if you'd write generic code exporter, last option best. if need cover specific use case, i'd go using ==.