On non-builtin types, types.FunctionType and types.MethodType behave as expected:
>>> isinstance(MyClass.func, FunctionType)
True
>>> isinstance(MyClass.func, MethodType)
False
>>> isinstance(MyClass().func, FunctionType)
False
>>> isinstance(MyClass().func, MethodType)
True
However, on a built-in type, BuiltinFunctionType and BuiltinMethodType don't behave accordingly:
>>> isinstance(list.append, (FunctionType, MethodType,
... BuiltinFunctionType, BuiltinMethodType))
False <- Why??
>>> isinstance([].append, (FunctionType, MethodType))
False
>>> isinstance([].append, BuiltinFunctionType)
True <- Why??
>>> isinstance([].append, BuiltinMethodType)
True
现在这没有意义，对吗？有人可以解释吗？
EDIT: isinstance(list.append, MethodDescriptorType) == True. Can someone explain how MethodDescriptorType differs from BuiltinMethodType and why do we need it? The official documentation doesn't really say much.
BuiltinFunctionTypeandBuiltinMethodTypeare just different names referring to the same object:isinstance(list.append, BuiltinMethodType)is false because it's not a method (i.e. an instance method bound to some object). For custom classes the method binding happens throughobject.__getattribute__, so the functions defined with a class are just plain functions:and hence
isinstance(MyClass.func, FunctionType). This works because all functions are non-data descriptors:For builtin types these objects (e.g.
list.append) are also dedicated descriptors that handle the binding to their objects. Sox = []; x.appendreturns a bound method which was created by the descriptorlist.appendand bound to the objectx: