inspect.signature: Support duck-types of Python functions (Cython, for instance) #17159
diff --git a/Lib/inspect.py b/Lib/inspect.py
index 8de9892..bc7eace 100644
--- a/Lib/inspect.py
+++ b/Lib/inspect.py
@@ -1601,6 +1601,30 @@
obj in (type, object))
+def _signature_is_functionlike(obj):
+ # Internal helper to test if `obj` is a duck type of FunctionType.
+ # A good example of such objects are functions compiled with
+ # Cython, which have all attributes that a pure Python function
+ # would have, but have their code statically compiled.
+
+ if not callable(obj) or isclass(obj):
+ # All function-like objects are obviously callables,
+ # and not classes.
+ return False
+
+ name = getattr(obj, '__name__', None)
+ code = getattr(obj, '__code__', None)
+ defaults = getattr(obj, '__defaults__', _void) # Important to use _void ...
+ kwdefaults = getattr(obj, '__kwdefaults__', _void) # ... and not None here
+ annotations = getattr(obj, '__annotations__', None)
+
+ return (isinstance(code, types.CodeType) and
+ isinstance(name, str) and
+ (defaults is None or isinstance(defaults, tuple)) and
+ (kwdefaults is None or isinstance(kwdefaults, dict)) and
+ isinstance(annotations, dict))
+
+
def _signature_get_bound_param(spec):
# Internal helper to get first parameter name from a
# __text_signature__ of a builtin method, which should
@@ -1670,7 +1694,9 @@
if _signature_is_builtin(obj):
return Signature.from_builtin(obj)
- if isinstance(obj, types.FunctionType):
+ if isfunction(obj) or _signature_is_functionlike(obj):
+ # If it's a pure Python function, or an object that is duck type
+ # of a Python function (Cython functions, for instance), then:
return Signature.from_function(obj)
if isinstance(obj, functools.partial):
@@ -2071,7 +2097,9 @@
def from_function(cls, func):
'''Constructs Signature for the given python function'''
- if not isinstance(func, types.FunctionType):
+ if not (isfunction(func) or _signature_is_functionlike(func)):
+ # If it's not a pure Python function, and not a duck type
+ # of pure function:
raise TypeError('{!r} is not a Python function'.format(func))
Parameter = cls._parameter_cls