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up vote 4 down vote favorite

I wanted to match the numeric values of a string:

1,000 metric tonnes per contract month
Five cents ($0.05) per tonne
Five cents ($0.05) per tonne
1,000 metric tonnes per contract month

My current approach:

size = re.findall(r'(\d+(,?\d*).*?)', my_string)

What I get with my approach:

print size
[(u'1,000', u',000')]

As you can see, the number 1 was being cut out from the second element of the list, why is that? Also, could I get a hint as to how I can match the $0.05 terms?

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I've edited my code to include '$' as well. –  Ashwini Chaudhary Jun 20 '13 at 12:24

5 Answers 5

up vote 3 down vote accepted

Something like this:

>>> import re
>>>  strs = """1,000 metric tonnes per contract month
Five cents ($0.05) per tonne
Five cents ($0.05) per tonne
1,000 metric tonnes per contract month"""
>>> [m.group(0) for m in re.finditer(r'\$?\d+([,.]\d+)?', strs)]
['1,000', '$0.05', '$0.05', '1,000']

Demo : http://rubular.com/r/UomzIY3SD3

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This also matches 1,00000 and doesn't match 1,000.05. –  Tim Pietzcker Jun 20 '13 at 12:12
up vote 3 down vote

re,findall() returns a tuple of all the capturing groups for each match, and each set of normal parentheses generates one such group. Write your regex like this:

size = re.findall(r'\d{1,3}(?:,\d{3})*(?:\.\d+)?', my_string)

Explanation:

\d{1,3}      # One to three digits
(?:,\d{3})*  # Optional thousands groups
(?:\.\d+)?   # Optional decimal part

This assumes that all numbers have commas as thousands separators, i. e. no numbers like 1000000. If you need to match those too, use

size = re.findall(r'\d+(?:,\d{3})*(?:\.\d+)?', my_string)
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1  
This fails on simple numbers such as '1000'. –  larsmans Jun 20 '13 at 12:11
up vote 0 down vote

Try this regex:

(\$?\d+(?:[,.]?\d*(?:\.\d+)?)).*?

Live demo

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Have a look at my solution. –  NeverHopeless Jun 20 '13 at 12:26
up vote 0 down vote

Why are you grouping your regex? Try this r'\$?\d+,?\d*\.?\d*'

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up vote 0 down vote

I would try this regex:

r'[0-9]+(?:,[0-9]+)(?:.[0-9])?'

Add \$? at the beginning to optionally catch the $

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