Can you list the keyword arguments a function receives?

This will print names of all passable arguments, keyword and non-keyword ones:

def func(one, two="value"):
    y = one, two
    return y
print func.func_code.co_varnames[:func.func_code.co_argcount]

This is because first co_varnames are always parameters (next are local variables, like y in the example above).

So now you could have a function:

def get_valid_args(func, args_dict):
    '''Return dictionary without invalid function arguments.'''
    validArgs = func.func_code.co_varnames[:func.func_code.co_argcount]
    return dict((key, value) for key, value in args_dict.iteritems() 
                if key in validArgs)

Which you then could use like this:

>>> func(**get_valid_args(func, args))

---

if you really need only keyword arguments of a function, you can use the func_defaults attribute to extract them:

def get_valid_kwargs(func, args_dict):
    validArgs = func.func_code.co_varnames[:func.func_code.co_argcount]
    kwargsLen = len(func.func_defaults) # number of keyword arguments
    validKwargs = validArgs[-kwargsLen:] # because kwargs are last
    return dict((key, value) for key, value in args_dict.iteritems() 
                if key in validKwargs)

You could now call your function with known args, but extracted kwargs, e.g.:

func(param1, param2, **get_valid_kwargs(func, kwargs_dict))

This assumes that func uses no *args or **kwargs magic in its signature.

A little nicer than inspecting the code object directly and working out the variables is to use the inspect module.

>>> import inspect
>>> def func(a,b,c=42, *args, **kwargs): pass
>>> inspect.getargspec(func)
(['a', 'b', 'c'], 'args', 'kwargs', (42,))

If you want to know if its callable with a particular set of args, you need the args without a default already specified. These can be got by:

def get_required_args(func):
    args, varargs, varkw, defaults = inspect.getargspec(func)
    if defaults:
        args = args[:-len(defaults)]
    return args   # *args and **kwargs are not required, so ignore them.

Then a function to tell what you are missing from your particular dict is:

def missing_args(func, argdict):
    return set(get_required_args(func)).difference(argdict)

Similarly, to check for invalid args, use:

def invalid_args(func, argdict):
    args, varargs, varkw, defaults = inspect.getargspec(func)
    if varkw: return set()  # All accepted
    return set(argdict) - set(args)

And so a full test if it is callable is :

def is_callable_with_args(func, argdict):
    return not missing_args(func, argdict) and not invalid_args(func, argdict)

(This is good only as far as python's arg parsing. Any runtime checks for invalid values in kwargs obviously can't be detected.)