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Alucard's answer is exactly what I would do - the only thing I would add is that if you're using python, you'll need to either provide the regex as a raw string, or escape the '\'s. So, either
Code:
regex = re.compile(r"\((a, b|a|b)\)")
or
Code:
regex = re.compile("\\((a, b|a|b)\\)")
I mention this because it can be one of the more confusing features of python's regex handling.
You can also use python's string formatting to make your expressions a little more readable:
Code:
a = "Some RE string"
b = "Some other RE string"
regex = re.compile("\\(%s, %s|%s|%s\\)" % (a, b, a, b))
I had already done that using str.replace(). But this is so much neater! I am still new to Python (not to programming) and it's great when you pick up wee nuggets of information like that in passing.
Quote:
Originally Posted by Julian Andrews
Especially if your regex gets complicated and long, building individually testable components like a and b can help a lot.
My little snippet above was just one element of seven of a complex regular expression. from which I am extracting 12 named groups:
In the end I fudged my "(m, n)" element to aid duplicating my named groups (m and n each consist of 2 groups).
Code:
regex = re.compile(r'\(m?(, )?n?\)')
I might end up with empty brackets but it's not too much of a problem as long as I can extract the values I am after. The string I am parsing is auto-generated, so should be pretty well formed.
Just ran this monster over 340,000 records and it does the trick.
Last edited by hashbang#!; 02-02-2011 at 10:07 AM.
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