I came across something today that I considered very odd.

>>> import StringIO>>> def test(thing=StringIO.StringIO()):...   thing.write("test")...   print thing.getvalue()... >>> test()test>>> test()testtest>>> test()testtesttest>>> test()testtesttesttest>>> test()testtesttesttesttest

Before today I would have read the line

def test(thing=StringIO.StringIO()):

as:

Declare a function which, whose kwargs dictionary, when called has a newStringIO by default as the value for the key 'thing', and add it to the current scope.

but from the example I think it's more like:

Declare a function. Construct a dictionary with a newStringIO in it. Assign this to the default kwargs of the function and add the function to the current scope.

Is this the correct interpretation? Are there any other gotchas to be aware of for default kwargs?

• 1
  Are you looking for this?docs.python.org/reference/…

  S.Lott

  – S.Lott

  2011-04-21 15:22:22 +00:00

  CommentedApr 21, 2011 at 15:22
• What, you mean thebig statement in bold? Heh. Yes.

  Joe

  – Joe

  2011-04-21 15:23:22 +00:00

  CommentedApr 21, 2011 at 15:23

2 Answers2

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