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Summary

Bio::SeqIO::fasta - fasta sequence input/output stream

Package variables

Included modules

Inherit

Bio::SeqIO

Synopsis

Do not use this module directly. Use it via the Bio::SeqIO class.

Description

This object can transform Bio::Seq objects to and from fasta flat
file databases.
A method preferred_id_type() can be used to specify the type of ID
we would like to parse from the fasta line. By default 'display' is
used, which means it parses everything from the '>' to the first space
and makes that the 'display_id' for the sequence.
Can be one of:
- accession
- accession.version
- display
- primary

Methods

Methods description

 Title   : next_seq
 Usage   : $seq = $stream->next_seq()
 Function: returns the next sequence in the stream
 Returns : Bio::Seq object
 Args    : NONE

 Title   : preferred_id_type
 Usage   : $obj->preferred_id_type('accession')
 Function: Get/Set the preferred type of identifier to use in the ">ID" position
           for FASTA output.
 Returns : string, one of values defined in @Bio::SeqIO::fasta::SEQ_ID_TYPES.
           Default = $Bio::SeqIO::fasta::DEFAULT_SEQ_ID_TYPE ('display').
 Args    : string when setting. This must be one of values defined in 
           @Bio::SeqIO::fasta::SEQ_ID_TYPES. Allowable values:
           accession, accession.version, display, primary
 Throws  : fatal exception if the supplied id type is not in @SEQ_ID_TYPES.

 Title   : width
 Usage   : $obj->width($newval)
 Function: Get/Set the line width for FASTA output
 Returns : value of width
 Args    : newvalue (optional)

 Title   : write_seq
 Usage   : $stream->write_seq(@seq)
 Function: writes the $seq object into the stream
 Returns : 1 for success and 0 for error
 Args    : array of 1 to n Bio::PrimarySeqI objects

Methods code

BEGIN {

 $WIDTH = 60

}

sub _initialize {

  my($self,@args) = @_;
  $self->SUPER::_initialize(@args);  
  my ($width) = $self->_rearrange([qw(WIDTH)], @args);
  $width && $self->width($width);
  unless ( defined $self->sequence_factory ) {
      $self->sequence_factory(Bio::Seq::SeqFastaSpeedFactory->new());
  }

}

sub next_seq {

    my( $self ) = @_;
    my $seq;
    my $alphabet;
    local $/ = "\n>";
    return unless my $entry = $self->_readline;

    chomp($entry);
    if ($entry =~ m/\A\s*\Z/s)  { # very first one
	return unless $entry = $self->_readline;
	chomp($entry);
    }
    $entry =~ s/^>//;

    my ($top,$sequence) = split(/\n/,$entry,2);
    defined $sequence && $sequence =~ s/>//g;
#    my ($top,$sequence) = $entry =~ /^>?(.+?)\n+([^>]*)/s
#	or $self->throw("Can't parse fasta entry");

    my ($id,$fulldesc);
    if( $top =~ /^\s*(\S+)\s*(.*)/ ) {
	($id,$fulldesc) = ($1,$2);
    }
    
    if (defined $id && $id eq '') {$id=$fulldesc;} # FIX incase no space 
                                                   # between > and name \AE
    defined $sequence && $sequence =~ s/\s//g;	# Remove whitespace

    # for empty sequences we need to know the mol.type
    $alphabet = $self->alphabet();
    if(defined $sequence && length($sequence) == 0) {
	if(! defined($alphabet)) {
	    # let's default to dna
	    $alphabet = "dna";
	}
    } else {
	# we don't need it really, so disable
	$alphabet = undef;
    }

    $seq = $self->sequence_factory->create(
					   -seq         => $sequence,
					   -id          => $id,
					   # Ewan's note - I don't think this healthy
					   # but obviously to taste.
					   #-primary_id  => $id,
					   -desc        => $fulldesc,
					   -alphabet    => $alphabet,
					   -direct      => 1,
					   );




    # if there wasn't one before, set the guessed type
    unless ( defined $alphabet ) {
	$self->alphabet($seq->alphabet());
    }
    return $seq;

}

sub preferred_id_type {

    my ($self,$type) = @_;
    if( defined $type ) {
	if( ! grep lc($type) eq $_, @SEQ_ID_TYPES) {
	    $self->throw(-class=>'Bio::Root::BadParameter',
			 -text=>"Invalid ID type\" $type\". Must be one of: @SEQ_ID_TYPES");
	}
	$self->{'_seq_id_type'} = lc($type);
#	print STDERR "Setting preferred_id_type=$type\n";
    }
    $self->{'_seq_id_type'} || $DEFAULT_SEQ_ID_TYPE;
}

1;

}

sub width {

   my ($self,$value) = @_;
   if( defined $value) {
      $self->{'width'} = $value;
    }
    return $self->{'width'} || $WIDTH;

}

sub write_seq {

   my ($self,@seq) = @_;
   my $width = $self->width;
   foreach my $seq (@seq) {
       $self->throw("Did not provide a valid Bio::PrimarySeqI object") 
	   unless defined $seq && ref($seq) && $seq->isa('Bio::PrimarySeqI');

       my $str = $seq->seq;
       my $top;

       # Allow for different ids 
       my $id_type = $self->preferred_id_type;
       if( $id_type =~ /^acc/i ) {
	   $top = $seq->accession_number();
	   if( $id_type =~ /vers/i ) {
	       $top .= "." . $seq->version();
	   }
       } elsif($id_type =~ /^displ/i ) {
	   $top = $seq->display_id();
       } elsif($id_type =~ /^pri/i ) {
	   $top = $seq->primary_id();
       }

       if ($seq->can('desc') and my $desc = $seq->desc()) {
	   $desc =~ s/\n//g;
	   $top .= " $desc";
       }
       if(length($str) > 0) {
	   $str =~ s/(.{1,$width})/$1\n/g;
       } else {
	   $str = "\n";
       }
       $self->_print (">",$top,"\n",$str) or return;
   }

   $self->flush if $self->_flush_on_write && defined $self->_fh;
   return 1;

}

General documentation

User feedback is an integral part of the evolution of this and other
Bioperl modules. Send your comments and suggestions preferably to one
of the Bioperl mailing lists. Your participation is much appreciated.

  bioperl-l@bioperl.org            - General discussion
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Report bugs to the Bioperl bug tracking system to help us keep track
the bugs and their resolution. Bug reports can be submitted via the
web:

  http://bugzilla.bioperl.org/

Email: birney@ebi.ac.uk
lstein@cshl.org

Jason Stajich, jason-at-bioperl.org

The rest of the documentation details each of the object
methods. Internal methods are usually preceded with a _