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string.join is abysmally slow

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On Mon, 16 Apr 2001 10:59:11 +1200 (NZST), Graham Guttocks wrote:>Greetings,>>I've run into a performance problem in one of my functions, and wonder>if I could get some recommendations on how to speed things up.>>What I'm trying to do is read in a textfile containing e-mail>addresses, one per line, and use them to build a regular expression>object in the form "address1|address2|address3|addressN" to search>against.>>I'm using string.join to concatenate the addresses together, separated>by a `|'.  The problem is that string.join is unacceptably slow in>this task.  The following program takes 37 seconds on a PIII/700 to>process a 239-line file!Yes, the number one rule on optimization is not to make assumptions but toprofile instead :-) I didn't do that, but I would bet it's the re.compile beingcalled 239 times that wastes the most time. Just do one re.compile after havingbuilt the regular expression and it should be a lot faster.Gerhard>>-------------------------------------------------------------------->>import fileinput, re, string>list = []>>for line in fileinput.input(textfile):>    # Comment or blank line?>    if line == '' or line[0] in '#':>        continue>    else:>        list.append(string.strip(line))>        # "address1|address2|address3|addressN">        regex = string.join(list,'|')>        regex = '"' + regex + '"'>        reo = re.compile(regex, re.I)-- mail:   gerhard <at> bigfoot <dot> deweb:http://highqualdev.com

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