How to properly use for-loop with python's regex library?

Question

I am trying to implement a program that will take a file, find all the regex matches associated with the document, and concatnate specific matches I want into a single string, which is written onto a file.

import re
import sys

f = open ('input/' + sys.argv[1], "r")
fd = f.read()
s = ''

pattern = re.compile(r'(?:(&#\d*|>))(.*?)(?=(&#\d*|<))')

for e in re.findall(pattern, fd, re.S)
        s += e[1]

f.close()
o = open ( 'output' + sys.argv[1], 'w', 0)
o.write(s)
o.close()

However, when I try to run this, I get the following error:

 File "./regex.py", line 8
    for e in re.findall(pattern, fd, re.S)

If

The error message is missing from your question.

dsh
– dsh

2015-07-30 21:00:01 +00:00
Commented Jul 30, 2015 at 21:00 — dsh
– dsh, Commented Jul 30, 2015 at 21:00

Eli Rose · Accepted Answer · 2015-07-30 20:58:39Z

1

You forgot a colon at the end of that line.

for e in re.findall(pattern, fd, re.S):

You seem to have chopped off the type of the error (SyntaxError, I imagine) but that information is very helpful. Seeing SyntaxError instead of some other type would let you know that your error has nothing to do with regexes.

answered Jul 30, 2015 at 20:58

Eli Rose

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Comments

plamut · Accepted Answer · 2015-07-30 22:45:14Z

0

Not directly related to the original question (it was indeed a missing colon), but I suggest to take a different approach to string concatenation. Repeatedly appending new chunks will create a new string each time (because strings are immutable). A better way would be to create an accumulator list, append each matched string to it and then join these strings into a single one using ''.join(my_list_with_matches).

answered Jul 30, 2015 at 22:45

plamut

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