Find which arguments of a method have defaults and add them to kwargs if they're not None.

kwargs.py

from __future__ import print_function

import inspect
import pprint


class MyClass(object):
    def myFunc(self, arg1, arg2=None, arg3=None, *args, **kwargs):
        # Find which arguments of this method have defaults and add them to kwargs if they're not None

        # Problem: locals() doesn't tell us that arg2 was declared with a default
        localVariables = locals()
        print('locals:', localVariables)
        # {'arg1': 'arg1', 'arg2': 'arg2', 'self': <__main__.MyClass object at...>, 'kwargs': {...}}

        # Problem: inspect.getargspec() will tell which arguments were declared and how many have defaults,
        # but it needs an object reference to this method (function), not just its name.
        # print('getargspec:', inspect.getargspec(self.myFunc)) # works, but need to put name of this function
        # print('getargspec:', inspect.getargspec('myFunc')) # TypeError: 'myFunc' is not a Python function

        # Problem: getting the name of this method is not very difficult,
        # but getting a reference to it is a little more work.

        frame = inspect.currentframe()
        thisMethodName = inspect.getframeinfo(frame).function
        thisMethod = inspect.getmembers(self, lambda x: inspect.ismethod(x) and x.__name__ == thisMethodName)[0][1]
        print('thisMethod:', thisMethod)

        argspec = inspect.getargspec(thisMethod)
        print('getargspec:', argspec)

        defaultsArgs = argspec.args[-len(argspec.defaults):]
        print('defaultsArgs:', defaultsArgs)

        print('kwargs before:', pprint.pformat(kwargs))

        print('filter:', filter(lambda (k, v): k in defaultsArgs and v is not None, localVariables.iteritems()))

        # Update kwargs with dictionary comprehension...
        # kwargs.update({k: v for (k, v) in localVariables.iteritems()
        #                if k in defaultsArgs and v is not None})

        # or...

        # Update kwargs with filter...
        kwargs.update(filter(lambda (k, v): k in defaultsArgs and v is not None, localVariables.iteritems()))

        print('kwargs after:', pprint.pformat(kwargs))

        # TODO: Move this to a function that may be used in any other function (or methods, at least)
        # In external function, locals will not be available, so it will need to be passed in or
        # gotten from the frame.


if __name__ == '__main__':
    myClass = MyClass()
    myClass.myFunc('arg1', arg2='arg2', fubar='snafu', fu=None)
    # print(inspect.getargspec(MyClass.myFunc))
    # print(inspect.getargspec(myClass.myFunc))