Too Many if Statements?

[Nicola Musatti]

bruno at modulix wrote:
[...]
> Suppose you have to match a line against a list of regexp and log if it
> doesn't match. You could of course repeat the whole code for each
> regexp, ie:
>
> if not re.match(r'a/regexp/here', line):
>   log('a first message')
>
> if not re.match(r'another/regexp/here', line):
>   log('another message')
>
> (... 150 regexps later ...)
>
> if not re.match(r'150/regexps/later', line):
>   log('pfww, getting tired of copy/pasting')
>
> etc...
>
> But you could also factor much of it:
>
> def checkMatch(line, regexp, msg):
>   if not re.match(regexp, line):
>     log(msg)
>
> then have a list of regexps/messages pairs and:
>   for exp, msg in regexps:
>     checkMatch(line, exp, msg)
>
> And now, you can add as many thousands regexps you want, you still have
> one (and only one) if in the code (well, in this snippet at least...).

If your checks are this complicated, I think you should consider
writing a parser for your configuration file. If you use a parser
generator it's not that difficult. Moreover a lexical analyzer could be
enough if your syntax is simple. I found Dave Beazley's PLY reasonably
easy to use: http://www.dabeaz.com/ply/

Cheers,
Nicola Musatti