[Bioperl-l] genbank parsing of multiple 'function' tags within primary tag

Fields, Christopher J cjfields at illinois.edu
Thu Sep 8 14:27:06 EDT 2011

On Sep 8, 2011, at 12:51 PM, galeb abu-ali wrote:

> thanks, Chris! works perfect. 
> To make sure I understand what's going on, forcing list context on $locus allows me to get one value at a time,...

You have to be careful in this circumstance; doing this:

   my $foo = @bar;

is scalar context on a list, which returns the number of elements in @bar.  The following

   my ($foo) = @bar;

forces list context and assigns the first value in @bar to $foo but tosses the rest.  If you are sure there is only one value in @bar anyway, the above is fine (and is a common perl idiom).  

> which is then concatenated with \t to concatenated functions. 

I'm just using a simple join() to print off the results.  Note the second element in the join list is an embedded join() with comma-sep values for functions.


> thanks again!
> galeb
> On Thu, Sep 8, 2011 at 12:51 PM, Fields, Christopher J <cjfields at illinois.edu> wrote:
> There is no need to do that if one is using the Bio::SeqFeatureI interface.  Note that get_tag_values always returns a list, so to snag a single value for a tag in a scalar, force list context on the LHS by enclosing the variable in ().
> chris
> -----------------------------
> #!/usr/bin/env perl
> use Modern::Perl;
> use Bio::SeqIO;
> my $in = Bio::SeqIO->new(-format => 'genbank',
>                         -file => shift);
> while (my $seq = $in->next_seq) {
>   for my $feat ($seq->get_SeqFeatures) {
>       next unless $feat->primary_tag eq 'CDS';
>       my ($locus) = $feat->has_tag('locus_tag') ?
>                     $feat->get_tag_values('locus_tag') : '';
>       my @funcs = $feat->has_tag('function') ?
>           $feat->get_tag_values('function') : ();
>       say join("\t", $locus, join(',', at funcs));
>   }
> }

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