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POHow can I detect if the caller passed any variables to my function in Python?
 

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  1. POHow can I detect if the caller passed any variables to my function in Python?
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    <p>I guess the subject sounds pretty stupid, so I'll show some code:</p> <pre><code>def foo(**kwargs): # How can you detect the difference between (**{}) and ()? pass foo(**{}) foo() </code></pre> <p>Is there any way to detect inside of foo, how the method was called?</p> <h3>Update 1</h3> <p>Because there were some comments why you possible want to do something, I'll try to explain some background.</p> <p><code>super(MyClass, self).foo(*args, **kwargs)</code> sucks - a lot of wasteful duplication. I want to write 'self.super()'. In this case, just call the super class and hand over all parameters that the calling method got as well. Works like a charm.</p> <p>Now the problematic magic part:</p> <p>I want to say 'self.super(something)' and in this case, only 'something' is passed to the super method. Works for most cases.</p> <p>This is where it breaks:</p> <pre><code>def foo(self, fnord=42, *args, **kwargs): self.super(*args, **kwargs) </code></pre> <p>So the super method should get the arguments that the calling method - however if <code>*args</code>, <code>**kwargs</code> are empty, currently the library can not detect this condition and passed all arguments including 'fnord'...</p> <p>Of course I could use <code>self.super.foo(*args, **kwargs)</code> as an alternative syntax but that's lame :-)</p> <p>PS: Yes, I know p3k's super, but still not nice and it does not work with Python 2.x...</p> <h3>Update 2</h3> <p>Actually even Python's ast module removes the <code>**{}</code> (<code>ast.parse('foo(**{})')</code>) so it looks like this happens so early in the parsing process that you can not get this information later on...</p> <p>So in the end I have either to give up on that specific problem (raising an AmbiguousSyntaxError) or to use text parsing as proposed by ~unutbu. Re-thinking my approach, the latter might actually feasable because I only need to know if it is <code>self.super(\s*)</code>, <code>self.super(\S+)</code>.</p>
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    1. USFelix Schwarz
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      1. POHow can I detect if the caller passed any variables to my function in Python?
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    1. COHow can it possibly matter?
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    2. COthey are same, except syntactic sugar, why it should matter anyway.
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      1. POHow can I detect if the caller passed any variables to my function in Python?
      1. USAnurag Uniyal
    3. COYou're right - usually it's not important. However I wrote a small module to simplify super calls which works really nice. However it has one part of magic in it and that breaks in the case above. Before I'm abadoning this nice pet project, I hoped that there are some gurus that can help me on this matter :-) Yes, I know that Python is about 'explicit, not implicit' - but I'd be glad if I did not have to argue about the value of my module in this thread :-)
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      1. USFelix Schwarz
 

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