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Working with Windows API which usually takes like a zillion for each function can be a little bit frustrating and if I want to only change two in the middle for each call I had to wrap everything into lambda functions which change arguments to the order that I need to use with partial.

So finally I added kinda dangerous decorator which inserts keywords into right position if detected and was about to use it but ctypes functions don't accept keyword arguments :D so just ended up with decorator :)

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from functools import partial
from inspect import getargspec, ismethod

def keywords_first(f):
    def wrapper(*a, **k):
        a = list(a)
        #for idx, arg in enumerate(f.func_code.co_varnames[:f.func_code.co_argcount], -ismethod(f)):
        for idx, arg in enumerate(getargspec(f).args, -ismethod(f)): # or [0] in 2.5
            if arg in k:
                if idx < len(a):
                    a.insert(idx, k.pop(arg))
                else:
                    break
        return f(*a, **k)
    return wrapper

@keywords_first
def fun(a, b, c=3): return a, b, c

print fun(1, 3, b=2) # normally: TypeError: f() got multiple values for keyword argument 'b'

def fun2(a, b, *args, **kwargs): return a, b, args, kwargs

print partial(keywords_first(fun2), a=1, c=2, b=2)(3, 4, 5, 6, 7) # noramlly: TypeError ...

def kfpartial(fun, *args, **kwargs):
    return partial(keywords_first(fun), *args, **kwargs)
   
print kfpartial(fun2, a=1, b=2)(3, 4, 5, 6, 7, c=3)

I'm not sure if it is all that useful, but makes the code shorter in some situations, especially when you have to pass handler and some default/reserved values around the code. EDIT: added ismethod to handle better methods and skip self argument

2 comments

obernard78+activestate 10 years, 1 month ago  # | flag

Nice. I always wanted to have a "shuffled" partial to apply to functions in operator module but the getargspec function does not work on built-in functions. :(

Nice recipe nonetheless.

Przemyslaw Podczasi (author) 9 years, 6 months ago  # | flag

With build-ins works in pypy. So if you don't have any specific libraries that hasn't been ported yet, you could switch.

Created by Przemyslaw Podczasi on Wed, 26 Oct 2011 (MIT)
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