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Comment by TylerE | Hacker News Reader

No he doesn't. defaultdict provides a default value for ALL missing values. His approach allows him to target one key in particular, and is a very common python idiom.

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I'm confused - where does that come from?

  >>> x.getDefault(1, 'Que?')

  Traceback (most recent call last):
    File "<pyshell#2>", line 1, in <module>
      x.getDefault(1, 'Que?')
  AttributeError: 'dict' object has no attribute 'getDefault'

Because it's actually (somewhat confusingly, called setdefault).

    >>> a = {1:'foo',2:'blah'}
    >>> a.setdefault(1,'default')
    'foo'
    >>> a.setdefault(4,'default')
    'default'
    >>> a
    {1: 'foo', 2: 'blah', 4: 'default'}

This actually updates the underlying datastructure. Very handy when you want to deal with nested structures, since you can do something like:

    matches.setdefault(keyword,[]).append(s)

This will append s to the list in matches[keyword] if it exists, or set matches[keyword] to [] and then append.

Wops, you both are right, thanks for pointing it out. I meant to say dict.get, i.e.

  {'a':1}.get('b',5)

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