Getting rid of an optional space in Python regex script

Question

I'm having a bit of an issue with my regex script and hopefully somebody can help me out.

Basically, I have a regex script that I use re.findall() with in a python script. My goal is to search various strings of varying length for references to Bible verses (e.g. John 3:16, Romans 6, etc). My regex script mostly works, but it sometimes tacks on an extra whitespace before the Bible book name. Here's the script:

versesToFind = re.findall(r'\d?\s?\w+\s\d+:?\d*', str)

To hopefully explain this problem better, here's my results when running this script on this text string:

str = 'testing testing John 3:16 adsfbaf John 2 1 Kings 4 Romans 4'

Result (from www.pythonregex.com):

[u' John 3:16', u' John 2', u'1 Kings 4', u' Romans 4']

As you can see, John 2 and Romans 4 has an extra whitespace at the beginning that I want to get rid of. Hopefully my explanation makes sense. Thanks in advance!

Jared · Accepted Answer · 2013-08-11 02:35:27Z

1

You can make the digit and space optional as a single unit by grouping with parens (?: just to specify it's non-capturing),

'(?:\d\s)?\w+\s\d+:?\d*'
 ^^^    ^

Which produces,

>>> s = 'testing testing John 3:16 adsfbaf John 2 1 Kings 4 Romans 4'
>>> re.findall(r'(?:\d\s)?\w+\s\d+:?\d*', s)
['John 3:16', 'John 2', '1 Kings 4', 'Romans 4']

answered Aug 11, 2013 at 2:35

Jared

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2 Comments

Matthieu Grieger Over a year ago

That works perfectly, thank you! I was trying to do exactly this but I didn't know the syntax for it.

Jared Over a year ago

@Matthieu Glad to help! Good to refer to docs.python.org/2/library/re.html

Bryan · Accepted Answer · 2013-08-11 02:38:20Z

0

Using list comprehension you can do it in a single line:

versesToFind = [x.strip() for x in re.findall(r'\d?\s?\w+\s\d+:?\d*', str)]

answered Aug 11, 2013 at 2:38

Bryan

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TerryA · Accepted Answer · 2013-08-11 03:09:26Z

0

Instead of rewriting your regular expression, you can always just strip() the whitespace:

>>> L = [u' John 3:16', u' John 2', u'1 Kings 4', u' Romans 4']
>>> print map(unicode.strip, L)
[u'John 3:16', u'John 2', u'1 Kings 4', u'Romans 4']

map() here is just identical to:

>>> print [i.strip() for i in L]
[u'John 3:16', u'John 2', u'1 Kings 4', u'Romans 4']

edited Aug 11, 2013 at 3:09

answered Aug 11, 2013 at 2:30

TerryA

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