Recognising whether a method is written in Python or Cython

Question

I have a function which receives a method. I would like to recognise whether this method is written in Python or in Cython. Is there some reliable way to do this?

Answer 1

Just a thought but, assuming that "pure Python" means "not built-in" where the term “built-in” means “written in C” (according to Python's documentation):

We could then distinguish those two kinds by doing:

>>> import types
>>> types.BuiltinFunctionType
<type 'builtin_function_or_method'>

This is not C-compiled function :

>>> def foo(x):
...     pass
>>> isinstance(foo, types.BuiltinFunctionType)
False

This is C-compiled function :

>>> from numpy import array
>>> isinstance(array, types.BuiltinFunctionType)
True

So any third-party module with C extensions will also report its functions as type builtin_function_or_method.

Related link:

• http://docs.python.org/2/library/types.html

EDIT :

Another idea (a dirty one, but as Sage is not cooperative...):

>>> def foo(x):
...     pass
>>> foo.some_attr = 0

is accepted, while:

>>> array.some_attr = 0
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'builtin_function_or_method' object has no attribute 'some_attr'

Hoping this can be helpful... You tell me.