Determine keywords of a tornado coroutine

Question

I want to inspect a Tornado coroutine to see if it has certain keywords. Normally I would do this with the inspect module, and in particular inspect.signature , which works great. However in Python 2 (I have to support both) signature doesn't exist, so I'm looking for an alternative. The standard inspect.getargspec doesn't work as desired.

In [1]: import inspect

In [2]: import tornado.gen

In [3]: class Foo(object):
   ...:     def a(self, x, y=None):
   ...:         pass
   ...:     
   ...:     @tornado.gen.coroutine
   ...:     def b(self, x, y=None):
   ...:         pass
   ...:     

In [4]: foo = Foo()

In [5]: inspect.getargspec(foo.a)
Out[5]: ArgSpec(args=['self', 'x', 'y'], varargs=None, keywords=None, defaults=(None,))

In [6]: inspect.getargspec(foo.b)
Out[6]: ArgSpec(args=[], varargs='args', keywords='kwargs', defaults=None)

In [7]: import sys; sys.version_info
Out[7]: sys.version_info(major=2, minor=7, micro=14, releaselevel='final', serial=0)

Is there a way, in Python 2, to answer questions like "does foo.b have a parameter named y ?"

Answer 1

There is nothing in the Python 2 standard library that can do this (but as you noted on Python 3 it works fine). You'll need to access the __wrapped__ attribute yourself. As suggested in Martijn Pieters' answer to a similar question, you could use a copy of the inspect.unwrap function from Python 3 or a simplified version like

def unwrap(func):
    while hasattr(func, '__wrapped__'):
        func = func.__wrapped__
    return func