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Re^5: Nested greps w/ Perl

by kennethk (Abbot)
on Dec 20, 2016 at 17:07 UTC ( [id://1178226]=note: print w/replies, xml ) Need Help??


in reply to Re^4: Nested greps w/ Perl
in thread Nested greps w/ Perl

If I were going to do what you say, I might write something like:
#!/usr/bin/perl use strict; use warnings; use 5.10.0; my %count; while (<DATA>) { if (/^(\S+)\s+([A-Z])$/) { $count{$1}{$2}++; } else { warn "Regular expression failed on $_"; } } for my $name (sort keys %count) { if (exists $count{$name}{Z}) { say "$name $count{$name}{Z}" } } __DATA__ Tommy Z Tommy Z Chris Z Chris B Chris Z Jake Z Jake Y
Important elements are keeping the line parsing code tight and minimizing the global memory footprint. Post more realistic data, and we can help refine regular expressions. Also note you are optimizing without profiling. In your circumstance, I will usually grab the first 1000 lines, and test my code with Devel::NYTProf to figure out if I'm doing something silly.

If you run something like the above on your file, the code should take about as long as just running

#!/usr/bin/perl use strict; use warnings; use 5.10.0; my $count; while (<DATA>) { $count++ } say $count;
If just counting lines in this way is too slow for your need, you'll need to use the window technique I and LanX have mentioned.

#11929 First ask yourself `How would I do this without a computer?' Then have the computer do it the same way.

Replies are listed 'Best First'.
Re^6: Nested greps w/ Perl
by wackattack (Sexton) on Dec 20, 2016 at 22:44 UTC
    I got it. Thank you!!!!!!!!!!!!!!!!

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