Question

I very new to Python, and fairly new to regex. (I have no Perl experience.)

I am able to use regular expressions in a way that works, but I’m not sure that my code is particularly Pythonic or consise.

For example, If I wanted to read in a text file and print out text that appears directly between the words ‘foo’ and ‘bar’ in each line (presuming this occurred one or zero times a line) I would write the following:

fileList = open(inFile, 'r')
pattern = re.compile(r'(foo)(.*)(bar)')
for line in fileList:
    result = pattern.search(line)
    if (result != None):
        print result.groups()[1]

Is there a better way? The if is necessary to avoid calling groups() on None. But I suspect there is a more concise way to obtain the matching String when there is one, without throwing errors when there isn’t.

I’m not hoping for Perl-like unreadability. I just want to accomplish this common task in the commonest and simplest way.

Answer 1

I think it’s fine.

Some minor points:-

• You can replace result.groups()[x] with result.group(x+1).
• If you don’t need to capture foo and bar, just use r'foo(.*)bar'.
• If you’re using Python 2.5+, try to use the with statement so even when there’s exception the file can be closed properly.

---

BTW, as a 5-liner (not that I recommend this):

import re
pattern = re.compile(r'foo(.*)bar')
with open(inFile, 'r') as fileList:
  searchResults = (pattern.search(line) for line in fileList)
  groups = (result.group(1) for result in searchResults if result is not None)
  print '\n'.join(groups)