4 ms·

I've finally decided that regular expressions are not witchcraft and that I need to learn how to use them.

kelukelugames 12y ago
I spent an entire day trying to decipher how to replace spaces with tabs. Wish I had been better with regular expressions.
- gknoy 12y ago
  I hope this isn't flippant, but have you read the Perl regex man pages [0]? "Perl compatible" regexes are very common, and are explained _really_ well. Similarly, the Perl Cookbook (from O'Reilly) has a whole chapter on regular expressions -- even crazy ones like detecting US phone numbers (hard!) -- with explanations. That chapter is QUITE good, and I highly recommend it even you don't write Perl. For your specific problem at hand, I assume you want to replace spaces with a tab character. In Perl, you could do: # replace four spaces with a tab, globally $line =~ s/ /\t/g; You can do this directly on the command line as well: perl -e 'while (<>) { $line = $_; $line =~ s/ /\t/g; print $line; }' < foo_spaces.py > foo_tabs.py I have a gist [1] which has very slightly more comments, if you prefer. To paraphrase XKCD, there are now N+1 regex explanations, and I apologize that mine is comparatively worse than all of them. :) 0: http://perldoc.perl.org/perlre.html http://perldoc.perl.org/perlre.html 1: https://gist.github.com/gknoy/94c382299c4543f2e863 https://gist.github.com/gknoy/94c382299c4543f2e863
  - kelukelugames 12y ago
    Thanks for sharing the man page link. I am reading it now! :)
  - deleted 12y ago
    [deleted]
- japhyr 12y ago
  Have you looked at sed yet?
  - kelukelugames 12y ago
    Sed was the problem. On Mac the syntax is slightly different and it doesn't take \t as tab. Those two curve balls took some extra research. I didn't actually take the entire day. :)
mercnet 12y ago
Any recommendations on learning them, e.g. tutorials?
- pc86 12y ago
  Not helpful at all for learning, but I've found RegExper[1] is fantastic for visualizing existing expressions, particularly ones you haven't written but need to understand or edit. [1] http://www.regexper.com/ http://www.regexper.com/
  - tovmeod 12y ago
    I like http://www.debuggex.com/ http://www.debuggex.com/
- mdibaiee 12y ago
  for JavaScript devs: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Regular_Expressions https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guid... also http://overapi.com/regex http://overapi.com/regex
- j13z 12y ago
  This is also a great tool to play around with / construct regexes: http://regex101.com/ http://regex101.com/
bbcbasic 12y ago
Tip: You don't have to put the entire expression in one line

I spent an entire day trying to decipher how to replace spaces with tabs. Wish I had been better with regular expressions.

gknoy 12y ago
I hope this isn't flippant, but have you read the Perl regex man pages [0]? "Perl compatible" regexes are very common, and are explained _really_ well. Similarly, the Perl Cookbook (from O'Reilly) has a whole chapter on regular expressions -- even crazy ones like detecting US phone numbers (hard!) -- with explanations. That chapter is QUITE good, and I highly recommend it even you don't write Perl. For your specific problem at hand, I assume you want to replace spaces with a tab character. In Perl, you could do: # replace four spaces with a tab, globally $line =~ s/ /\t/g; You can do this directly on the command line as well: perl -e 'while (<>) { $line = $_; $line =~ s/ /\t/g; print $line; }' < foo_spaces.py > foo_tabs.py I have a gist [1] which has very slightly more comments, if you prefer. To paraphrase XKCD, there are now N+1 regex explanations, and I apologize that mine is comparatively worse than all of them. :) 0: http://perldoc.perl.org/perlre.html http://perldoc.perl.org/perlre.html 1: https://gist.github.com/gknoy/94c382299c4543f2e863 https://gist.github.com/gknoy/94c382299c4543f2e863
- kelukelugames 12y ago
  Thanks for sharing the man page link. I am reading it now! :)
- deleted 12y ago
  [deleted]
japhyr 12y ago
Have you looked at sed yet?
- kelukelugames 12y ago
  Sed was the problem. On Mac the syntax is slightly different and it doesn't take \t as tab. Those two curve balls took some extra research. I didn't actually take the entire day. :)

mercnet 12y ago

Any recommendations on learning them, e.g. tutorials?

pc86 12y ago
Not helpful at all for learning, but I've found RegExper[1] is fantastic for visualizing existing expressions, particularly ones you haven't written but need to understand or edit. [1] http://www.regexper.com/ http://www.regexper.com/
- tovmeod 12y ago
  I like http://www.debuggex.com/ http://www.debuggex.com/
mdibaiee 12y ago
for JavaScript devs: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Regular_Expressions https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guid... also http://overapi.com/regex http://overapi.com/regex
j13z 12y ago
This is also a great tool to play around with / construct regexes: http://regex101.com/ http://regex101.com/

bbcbasic 12y ago

Tip: You don't have to put the entire expression in one line