elegant. :) simple yet elegant.
> Date: Sun, 23 Jan 2011 14:10:35 +1100 > From: st...@pearwood.info > To: tutor@python.org > Subject: Re: [Tutor] Help on RE > > tee chwee liong wrote: > > thanks for making me understand more on re. re is a confusing topic as i'm > > starting on python. > > I quote the great Jamie Zawinski, a world-class programmer and hacker: > > Some people, when confronted with a problem, think 'I know, I'll > use regular expressions." Now they have two problems. > > > Zawinski doesn't mean that you should never use regexes. But they should > be used only when necessary, for problems that are difficult enough to > require a dedicated domain-specific language for solving search problems. > > Because that's what regexes are: they're a programming language for text > searching. They're not a full-featured programming language like Python > (technically, they are not Turing Complete) but nevertheless they are a > programming language. A programming language with a complicated, > obscure, hideously ugly syntax (and people complain about Forth!). Even > the creator of Perl, Larry Wall, has complained about regex syntax and > gives 19 serious faults with regular expressions: > > http://dev.perl.org/perl6/doc/design/apo/A05.html > > Most people turn to regexes much too quickly, using them to solve > problems that are either too small to need regexes, or too large. Using > regexes for solving your problem is like using a chainsaw for peeling an > orange. > > Your data is very simple, and doesn't need regexes. It looks like this: > > > Platform: PC > Tempt : 25 > TAP0 :0 > TAP1 :1 > +++++++++++++++++++++++++++++++++++++++++++++ > Port Chnl Lane EyVt EyHt > +++++++++++++++++++++++++++++++++++++++++++++ > 0 1 1 75 55 > 0 1 2 10 35 > 0 1 3 25 35 > 0 1 4 35 25 > 0 1 5 10 -1 > +++++++++++++++++++++++++++++++++++++++++++++ > Time: 20s > > > The part you care about is the table of numbers, each line looks like this: > > 0 1 5 10 -1 > > The easiest way to parse this line is this: > > numbers = [int(word) for word in line.split()] > > All you need then is a way of telling whether you have a line in the > table, or a header. That's easy -- just catch the exception and ignore it. > > template = "Port=%d, Channel=%d, Lane=%d, EyVT=%d, EyHT=%d" > for line in lines: > try: > numbers = [int(word) for word in line.split()] > except ValueError: > continue > print(template % tuple(numbers)) > > > Too easy. Adding regexes just makes it slow, fragile, and difficult. > > > My advice is, any time you think you might need regexes, you probably don't. > > > -- > Steven > > _______________________________________________ > Tutor maillist - Tutor@python.org > To unsubscribe or change subscription options: > http://mail.python.org/mailman/listinfo/tutor
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