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Title: Splitting up a sequence
Submitter: Guyon Morée
(other recipes)
Last Updated: 2005/06/08
Version no: 1.3
Category:
Algorithms
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 1 vote(s)
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Description:
Split up a sequence in same-size(if possible) parts.
Source: Text Source
def split_seq(seq,size):
""" Split up seq in pieces of size """
return [seq[i:i+size] for i in range(0, len(seq), size)]
Discussion:
As discussed on: http://gumuz.looze.net/wordpress/index.php/archives/2005/04/20/python-chopping-up-a-sequence/
It's very straight forward:
>>> lst = [1,2,3,4,5,6,7,8,9,10]
>>> split_seq(lst,2)
[[1, 2], [3, 4], [5, 6], [7, 8], [9,10]]
It takes a list, re-groups them in another list, 2 items per group. The source list doesn't have to be evenly dividable though:
>>> lst = [1,2,3,4,5,6,7,8,9,10]
>>> split_seq(lst,3)
[[1, 2, 3], [4, 5, 6], [7, 8, 9], [10]]
Of course, a string is a sequence too. That's what I used it for last time. I had a string of bits, which I needed to divide in pieces of 8, bytes:
>>> bits = '101011101001011010010110'
>>> split_seq(bits,8)
['10101110', '10010110', '10010110']
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Number of comments: 4
Nick Matsakis, 2005/06/08
One issue with this recipe is that you wind up with a list at the end that could be much shorter than what you have. Consider this alternative:
def split_seq(seq, size):
newseq = []
splitsize = 1.0/size*len(seq)
for i in range(size):
newseq.append(seq[int(round(i*splitsize)):int(round((i+1)*splitsize))])
return newseq
This produces the following results, which may be preferred for some applications:
>>> split_seq([1,2,3,4,5,6,7,8,9,10], 3)
[[1, 2, 3], [4, 5, 6, 7], [8, 9, 10]]
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very useful as well, Guyon Morée, 2005/06/09
Thanx Nick, that's a cool one as well. Do you want me to add your version to the recipe or are you going to add this as a recipe as well?
Cheers,
Guyon Morée
http://gumuz.looze.net/
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Nick Matsakis, 2005/06/10
I just submitted it as a separate recipe, though I'm not sure I like it so much. I wonder if it could be done using only integer math.
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Gene tani, 2005/06/21
There's variations on this:
http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/303279
http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/347689
http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/303060
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