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Korakot Chaovavanich http://korakot.stumbleupon.com

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Default dictionary

I always want to do this, like I did in Perl.
   1  
   2  >> d = DefaultDict(0)
   3  >> d[key] += 1     # no need to use d.get or d.setdefault
   4  
   5  >> d = DefaultDict([])  # similarly with list value
   6  >> d[key].append(item)

See the implementation by Peter Norvig (of AI & Google fame)
here
to python default dict by korakot on Sep 14, 2005

Counting characters in string

   1  
   2  >>> s = 'a;jfkd;aflhakfhaskfjalghlakfhfnkjafyksd'
   3  >>> cnt = {}
   4  >>> for c in s:
   5  	cnt[c] = cnt.get(c,0) + 1
   6  
   7  >>> print cnt
   8  {'a': 7, 'd': 2, 'g': 1, 'f': 7, 'h': 4, 'k': 6, 'j': 3, 'l': 3, 'n': 1, 's': 2, 'y': 1, ';': 2}

This can be used to count any distribution.
Note the use of dict.get(key,default) to set to 0
if the key is not avaiable.
If this were perl, I would just do a
   1  cnt[c] += 1

But python will give an error instead of returning 0.
It's not too bad, though.
to python count dictionary default by korakot on Jul 26, 2005 1 Comments
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