I’ve been working on a script that searches files based on regular expressions and came up with a pretty neat way to do this  – using filter! (this may be old hat to more experienced Python programers, but I am just starting to get comfortable with map/filter/etc…). In this example we compile our regex and filter the gzip file that we have read into memory and display the lines that match and the type of regex that they match on.

import re
import gzip

searchName = "Example Regex"
compiledRegex = re.compile(r'example' re.I)

dataFile = gzip.open(fileName, "rb")
#read in the file to memory
fullData = dataFile.readlines()
regexName = searchName
regexSearch = compiledRegex .search
#Filter for just the lines matching the regex
hitList = filter(regexSearch, fullData)
#hitList now is just a list of our matches
for item in hitList:
    print "MATCH:%s" % regexName
    print "ENTRY:%s" % item

Obviously this code needs more to be at all usable, but this is the general idea and a pretty cool use of the filter function.

If you know of a better way, let me know in the comments.

References:
Python Regular Expressions (re) : http://docs.python.org/library/re.html
Filter Function : http://docs.python.org/library/functions.html#filter