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Re: Pythonic way to count sequences

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On 4/25/13, Denis McMahon <denismfmcmahon@gmail.com> wrote:
> On Wed, 24 Apr 2013 22:05:52 -0700, CM wrote:
>
>> I have to count the number of various two-digit sequences in a list such
>> as this:
>>
>> mylist = [(2,4), (2,4), (3,4), (4,5), (2,1)]  # (Here the (2,4) sequence
>> appears 2 times.)
>>
>> and tally up the results, assigning each to a variable.
...

Consider using the ``collections`` module::


    from collections import Counter

    mylist = [(2,4), (2,4), (3,4), (4,5), (2,1)]
    count = Counter()
    for k in mylist:
        count[k] += 1

    print(count)

    # Output looks like this:
    # Counter({(2, 4): 2, (4, 5): 1, (3, 4): 1, (2, 1): 1})


You then have access to methods to return the most common items, etc. See more
examples here:

http://docs.python.org/3.3/library/collections.html#collections.Counter


Good luck!
-Modulok-

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Pythonic way to count sequences CM <cmpython@gmail.com> - 2013-04-24 22:05 -0700
  Re: Pythonic way to count sequences Chris Angelico <rosuav@gmail.com> - 2013-04-25 15:26 +1000
    Re: Pythonic way to count sequences CM <cmpython@gmail.com> - 2013-04-25 19:40 -0700
  Re: Pythonic way to count sequences Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-04-25 06:14 +0000
  Re: Pythonic way to count sequences Serhiy Storchaka <storchaka@gmail.com> - 2013-04-25 15:36 +0300
  Re: Pythonic way to count sequences Denis McMahon <denismfmcmahon@gmail.com> - 2013-04-25 23:29 +0000
    Re: Pythonic way to count sequences Modulok <modulok@gmail.com> - 2013-04-25 19:16 -0600
    Re: Pythonic way to count sequences Matthew Gilson <m.gilson1@gmail.com> - 2013-04-25 22:40 -0400

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