In Python how can one tell if a module comes from a C extension?

Question

What is the correct or most robust way to tell from Python if an imported module comes from a C extension as opposed to a pure Python module? This is useful, for example, i

Answer 1

While Cecil Curry's answer works (and was very informative, as was abarnert's, I might add) it will return False for the "top level" of a module even if it includes sub-modules that use the C extension (e.g. numpy vs. numpy.core.multiarray).

While probably not as robust as it could be, the following is working for my use current use cases:

def is_c(module):

    # if module is part of the main python library (e.g. os), it won't have a path
    try:
        for path, subdirs, files in os.walk(module.__path__[0]):

            for f in files:
                ftype = f.split('.')[-1]
                if ftype == 'so':
                    is_c = True
                    break
        return is_c

    except AttributeError:

        path = inspect.getfile(module)
        suffix = path.split('.')[-1]

        if suffix != 'so':

            return False

        elif suffix == 'so':

            return True

is_c(os), is_c(im), is_c(et), is_c_extension(ma), is_c(numpy)
# (False, False, True, True, True)