How to use Python's groupby

Question

How can I split a string on 2's, eg "string" would be split into groups of "st", "ri","ng". I check the doc, groupby from itertools seems to be what i need. However, is there a way to do it simply by not using itertools? thanks

Also, http://stackoverflow.com/questions/434287/what-is-the-most-pythonic-way-to-iterate-over-a-list-in-chunks?lq=1 — Ilmo Euro, Sep 09 '13 at 04:33
See [this answer](http://stackoverflow.com/questions/434287/what-is-the-most-pythonic-way-to-iterate-over-a-list-in-chunks/434328#434328) for a non-itertools version. — Burhan Khalid, Sep 09 '13 at 05:13
This is the actual answer: http://stackoverflow.com/questions/12328108/how-can-i-split-a-string-in-python — Henrik Andersson, Sep 09 '13 at 06:10

score 2 · Accepted Answer · answered Sep 09 '13 at 04:42

2

You could do it without itertools, but it will be slower. Unless it's a learning excersize, use the "grouper" recipe from the itertools page:

def grouper(iterable, n, fillvalue=None):
    "Collect data into fixed-length chunks or blocks"
    # grouper('ABCDEFG', 3, 'x') --> ABC DEF Gxx
    args = [iter(iterable)] * n
    return izip_longest(fillvalue=fillvalue, *args)

answered Sep 09 '13 at 04:42

theodox

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Note that `izip_longest` requires Python 2.6+ – Ilmo Euro Sep 09 '13 at 04:48
I prefer [@nosklo's answer](http://stackoverflow.com/a/434328/790387) from the linked question since it doesn't have version restrictions – Burhan Khalid Sep 09 '13 at 05:12
Depending on Python 2.6, released in 2008, is hardly a serious version restriction. – user4815162342 Sep 09 '13 at 06:12
thanks. i guess if I compile my script to executable, it might not have version restrictions? – dorothy Sep 09 '13 at 07:26
@dorothy if you use `py2exe` or `freeze`, the version you're using is bundled with the program, so you don't have to worry about versions. – Ilmo Euro Sep 09 '13 at 07:44

score 1 · Answer 2 · edited Sep 09 '13 at 06:07

1

s='your input string'
ans=[  ]
i=0
while i < len(s):
    ans.append( s[ i:i+2 ] )
    i+=2
print ans

edited Sep 09 '13 at 06:07

Henrik Andersson

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answered Sep 09 '13 at 06:00

ayush1794

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score 0 · Answer 3 · answered Sep 09 '13 at 09:28

0

If you just want to do the two character groups without itertools, you can use this:

s = 'string'
groups = [''.join(g) for g in zip(s[:-1:2], s[1::2])]

Note that this only works properly for even-length strings.

answered Sep 09 '13 at 09:28

chthonicdaemon

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How to use Python's groupby

3 Answers3