bpo-41792: Add is_typeddict function to typing.py (GH-22254)
Closes issue41792.
Also closes https://github.com/python/typing/issues/751.
diff --git a/Doc/library/typing.rst b/Doc/library/typing.rst
index 3125ae9..bfff81e 100644
--- a/Doc/library/typing.rst
+++ b/Doc/library/typing.rst
@@ -1658,6 +1658,20 @@
.. versionadded:: 3.8
+.. function:: is_typeddict(tp)
+
+ Check if an annotation is a TypedDict class.
+
+ For example::
+ class Film(TypedDict):
+ title: str
+ year: int
+
+ is_typeddict(Film) # => True
+ is_typeddict(Union[list, str]) # => False
+
+ .. versionadded:: 3.10
+
.. class:: ForwardRef
A class used for internal typing representation of string forward references.
diff --git a/Lib/test/test_typing.py b/Lib/test/test_typing.py
index 05140fc..42aa430 100644
--- a/Lib/test/test_typing.py
+++ b/Lib/test/test_typing.py
@@ -16,6 +16,7 @@
from typing import cast, runtime_checkable
from typing import get_type_hints
from typing import get_origin, get_args
+from typing import is_typeddict
from typing import no_type_check, no_type_check_decorator
from typing import Type
from typing import NewType
@@ -3900,6 +3901,12 @@
'voice': str,
}
+ def test_is_typeddict(self):
+ assert is_typeddict(Point2D) is True
+ assert is_typeddict(Union[str, int]) is False
+ # classes, not instances
+ assert is_typeddict(Point2D()) is False
+
class IOTests(BaseTestCase):
diff --git a/Lib/typing.py b/Lib/typing.py
index 2aedbeb..8c61bd8 100644
--- a/Lib/typing.py
+++ b/Lib/typing.py
@@ -103,6 +103,7 @@
'get_args',
'get_origin',
'get_type_hints',
+ 'is_typeddict',
'NewType',
'no_type_check',
'no_type_check_decorator',
@@ -1479,6 +1480,20 @@
return ()
+def is_typeddict(tp):
+ """Check if an annotation is a TypedDict class
+
+ For example::
+ class Film(TypedDict):
+ title: str
+ year: int
+
+ is_typeddict(Film) # => True
+ is_typeddict(Union[list, str]) # => False
+ """
+ return isinstance(tp, _TypedDictMeta)
+
+
def no_type_check(arg):
"""Decorator to indicate that annotations are not type hints.
diff --git a/Misc/NEWS.d/next/Library/2020-09-15-07-55-35.bpo-41792.qMpSlU.rst b/Misc/NEWS.d/next/Library/2020-09-15-07-55-35.bpo-41792.qMpSlU.rst
new file mode 100644
index 0000000..fbbc672
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2020-09-15-07-55-35.bpo-41792.qMpSlU.rst
@@ -0,0 +1,6 @@
+Add is_typeddict function to typing.py to check if a type is a TypedDict
+class
+
+Previously there was no way to check that without using private API. See the
+`relevant issue in python/typing
+<https://github.com/python/typing/issues/751>`