Regex for matching string with trailing whitespace works in Perl but not Python

Question

I'm trying to find strings that have trailing whitespace, i.e. 'foo ' as opposed to 'foo'.

In Perl, I would use:

$str = 'foo ';
print "Match\n" if ($str =~ /\s+$/) ;

When I try this in Python 2.6, e.g.:

import re

str = 'foo '
if re.match('\s+$', str):
    print 'Match'

it doesn't match. I feel like I'm missing something obvious but I can't figure out what I'm doing wrong.

Answer 1

Use re.search() instead; re.match() only matches at the start of a string. Quoting the re.match() documentation:

If zero or more characters at the beginning of string match the regular expression pattern, return a corresponding MatchObject instance.

Emphasis mine.

In other words, re.match() is the equivalent of the m/.../ match operator in Perl, while re.search() is the same as /.../.

Answer 2

Because re.match(r'\s+$', str) is equivalent to re.search(r'\A\s+$', str). Use re.search instead.

From docs:

re.match() checks for a match only at the beginning of the string, while re.search() checks for a match anywhere in the string (this is what Perl does by default).