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Date: Tue, 27 Dec 2011 00:16:51 +0000
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Subject: Re: Regular expressions
From: Jason Friedman <jason@powerpull.net>
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> On Tue, Dec 27, 2011 at 10:45 AM, mauriceling@acm.org
> <mauriceling@gmail.com> wrote:
>> Hi
>>
>> I am trying to change <one string> to <another string>.
>>
>> Can anyone help me with the regular expressions needed?
>
> A regular expression defines a string based on rules. Without seeing a
> lot more strings, we can't know what possibilities there are for each
> part of the string. You probably know your data better than we ever
> will, even eyeballing the entire set of strings; just write down, in
> order, what the pieces ought to be - for instance, the first token
> might be a literal @ sign, followed by three upper-case letters, then
> a hyphen, then any number of alphanumerics followed by a colon, etc.
> Once you have that, it's fairly straightforward to translate that into
> regex syntax.
>
> ChrisA
> --
> http://mail.python.org/mailman/listinfo/python-list

The OP told me, off list, that my guess was true:

> Can we say that your string:
> 1) Contains 7 colon-delimited fields, followed by
> 2) whitespace, followed by
> 3) 3 colon-delimited fields (A, B, C), followed by
> 4) a colon?
> The transformation needed is that the whitespace is replaced by a
> slash, the "A" characters are taken as is, and the colons and fields
> following the "A" characters are eliminated?

Doubtful that my guess was 100% accurate, but nevertheless:

>>> import re
>>> string1 = "@HWI-ST115:568:B08LLABXX:1:1105:6465:151103 1:N:0:"
>>> re.sub(r"(\S+)\s+(\S+?):.+", "\g<1>/\g<2>", string1)
'@HWI-ST115:568:B08LLABXX:1:1105:6465:151103/1'