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Re: Reading file into a hash

by hippo (Abbot)
on May 28, 2014 at 14:51 UTC ( #1087661=note: print w/replies, xml ) Need Help??

in reply to Reading file into a hash

I think that the problem is that you are setting the value of $seq to be '' but then testing it via defined, which (other than the first time through) it will be. Change your test from if ( defined $seq ) to just if ($seq) and see what difference that makes.

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Re^2: Reading file into a hash
by PerlSufi (Friar) on May 28, 2014 at 14:53 UTC
    Hi hippo,
    Thanks for the response. I changed it and still did not get the last header and sequence
      Thats a very common problem, you are trying to add a record only when the successor is to be parsed, but the last record has no successor (sic ;)!

      Most people try to solve by repeating code to add the last record after the loop.

      But it's much cleaner this way (avoiding a posteriori state logic)

      use strict; use warnings; use Data::Dump; my $header; my %sequence; while ( my $line = <DATA> ){ chomp $line; if ( $line =~ /^>(.*)/ ) { $header = $1; } else { $sequence{$header} .= $line; } } dd \%sequence; __DATA__ >sequence_5849 CCTGCGGAAGATCGGCACTAGAATAGCCAGAACCGTTTCTCTGAGGCTTCCGGCCTTCCC TCCCACTAATAATTCTGAGG >sequence_5959 CCATCGGTAGCGCATCCTTAGTCCAATTAAGTCCCTATCCAGGCGCTCCGCCGAAGGTCT ATATCCATTTGTCAGCAGACACGC >sequence_0808 CCACCCTCGTGGTATGGCTAGGCATTCAGGAACCGGAGAACGCTTCAGACCAGCCCGGAC TGGGAACCTGCGGGCAGTAGGTGGAAT

      Cheers Rolf

      ( addicted to the Perl Programming Language)


      a *general pattern* to solve such problems while staying DRY is to use references

      if ( $line =~ /^(HEAD_PATTERN)/ ) { $data = \ $deeply{nested}{structure}{$1}; # reference data + } else { $$data .= $line; # derefrence data }

      like this you don't need to repeat the path of a deeply nested data structure, which might vary in multiple dimensions

      added some explanation

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