regex help: splitting string gets weird groups

Jon Clements joncle at googlemail.com
Thu Apr 8 21:44:33 CEST 2010


On 8 Apr, 19:49, gry <georgeryo... at gmail.com> wrote:
> [ python3.1.1, re.__version__='2.2.1' ]
> I'm trying to use re to split a string into (any number of) pieces of
> these kinds:
> 1) contiguous runs of letters
> 2) contiguous runs of digits
> 3) single other characters
>
> e.g.   555tHe-rain.in#=1234   should give:   [555, 'tHe', '-', 'rain',
> '.', 'in', '#', '=', 1234]
> I tried:>>> re.match('^(([A-Za-z]+)|([0-9]+)|([-.#=]))+$', '555tHe-rain.in#=1234').groups()
>
> ('1234', 'in', '1234', '=')
>
> Why is 1234 repeated in two groups?  and why doesn't "tHe" appear as a
> group?  Is my regexp illegal somehow and confusing the engine?
>
> I *would* like to understand what's wrong with this regex, though if
> someone has a neat other way to do the above task, I'm also interested
> in suggestions.

I would avoid .match and use .findall
(if you walk through them both together, it'll make sense what's
happening
with your match string).

>>> s = """555tHe-rain.in#=1234"""
>>> re.findall('[A-Za-z]+|[0-9]+|[-.#=]', s)
['555', 'tHe', '-', 'rain', '.', 'in', '#', '=', '1234']

hth,

Jon.



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