/ 
bioperl-1.5.2_004-RCb
/ Bio::FeatureIO

NAME

Bio::FeatureIO - Handler for FeatureIO

SYNOPSIS

use Bio::FeatureIO;

#read from a file
$in  = Bio::FeatureIO->new(-file => "my.gff" , -format => 'GFF');

#read from a filehandle
$in  = Bio::FeatureIO->new(-fh => \*GFF , -format => 'GFF');

#read features already attached to a sequence
my $feat = Bio::FeatureIO->new(-seq => $seq , -format => 'features');

#read new features for existing sequence
my $seq = Bio::FeatureIO->new(-seq => $seq , -format => 'Das');

#write out features
$out = Bio::FeatureIO->new(-file    => ">outputfilename" ,
                           -format  => 'GFF' ,
                           -version => 3);

while ( my $feature = $in->next_feature() ) {
  $out->write_feature($feature);
}

DESCRIPTION

An I/O iterator subsystem for genomic sequence features.

Bio::FeatureIO is a handler module for the formats in the FeatureIO set (eg, Bio::FeatureIO::GFF). It is the officially sanctioned way of getting at the format objects, which most people should use.

The Bio::FeatureIO system can be thought of like biological file handles. They are attached to filehandles with smart formatting rules (eg, GFF format, or BED format) and can either read or write feature objects (Bio::SeqFeature objects, or more correctly, Bio::FeatureHolderI implementing objects, of which Bio::SeqFeature is one such object). If you want to know what to do with a Bio::SeqFeatureI object, read Bio::SeqFeatureI.

The idea is that you request a stream object for a particular format. All the stream objects have a notion of an internal file that is read from or written to. A particular FeatureIO object instance is configured for either input or output. A specific example of a stream object is the Bio::FeatureIO::gff object.

Each stream object has functions:

$stream->next_feature();
$stream->write_feature($feature);

SUPPORTED FORMATS

name                         module
-----------------------------------
BED                          bed.pm
GFF                          gff.pm
GTF                          gtf.pm
InterPro (IPRScan 4.0)  interpro.pm
PTT (NCBI protein table)     ptt.pm

CONSTRUCTORS

Bio::FeatureIO->new()

$featureIO = Bio::FeatureIO->new(-file => 'filename',   -format=>$format);
$featureIO = Bio::FeatureIO->new(-fh   => \*FILEHANDLE, -format=>$format);
$featureIO = Bio::FeatureIO->new(-seq  => $seq,         -format=>$format);

The new() class method constructs a new Bio::FeatureIO object. The returned object can be used to retrieve or print Seq objects. new() accepts the following parameters:

-file

A file path to be opened for reading or writing. The usual Perl conventions apply:

'file'       # open file for reading
'>file'      # open file for writing
'>>file'     # open file for appending
'+<file'     # open file read/write
'command |'  # open a pipe from the command
'| command'  # open a pipe to the command
-fh

You may provide new() with a previously-opened filehandle. For example, to read from STDIN:

$featio = Bio::FeatureIO->new(-fh => \*STDIN);

Note that you must pass filehandles as references to globs.

If neither a filehandle nor a filename is specified, then the module will read from the @ARGV array or STDIN, using the familiar <> semantics.

A string filehandle is handy if you want to modify the output in the memory, before printing it out. The following program reads in EMBL formatted entries from a file and prints them out in fasta format with some HTML tags:

use Bio::FeatureIO;
use IO::String;
my $in  = Bio::FeatureIO->new('-file' => "my.gff" ,
			    '-format' => 'EMBL');
while ( my $f = $in->next_feature() ) {
    # the output handle is reset for every file
    my $stringio = IO::String->new($string);
    my $out = Bio::FeatureIO->new('-fh' => $stringio,
			        '-format' => 'gtf');
    # output goes into $string
    $out->write_feature($f);
    # modify $string
    $string =~ s|(>)(\w+)|$1<font color="Red">$2</font>|g;
    # print into STDOUT
    print $string;
}
-format

Specify the format of the file. See above for list of supported formats

-flush

By default, all files (or filehandles) opened for writing sequences will be flushed after each write_seq() (making the file immediately usable). If you don't need this facility and would like to marginally improve the efficiency of writing multiple sequences to the same file (or filehandle), pass the -flush option '0' or any other value that evaluates as defined but false:

my $f1 = new Bio::FeatureIO -file   => "<a.f1",
                            -format => "f1";
my $f2 = new Bio::FeatureIO -file   => ">a.f2",
                            -format => "f2",
                            -flush  => 0; # go as fast as we can!

while($feature = $f1->next_feature) { $f2->write_feature($feature) }

Bio::FeatureIO->newFh()

$fh = Bio::FeatureIO->newFh(-fh   => \*FILEHANDLE, -format=>$format);
$fh = Bio::FeatureIO->newFh(-format => $format);
# etc.

This constructor behaves like new(), but returns a tied filehandle rather than a Bio::FeatureIO object. You can read sequences from this object using the familiar <> operator, and write to it using print(). The usual array and $_ semantics work. For example, you can read all sequence objects into an array like this:

@features = <$fh>;

Other operations, such as read(), sysread(), write(), close(), and printf() are not supported.

OBJECT METHODS

See below for more detailed summaries. The main methods are:

$feature = $featureIO->next_feature()

Fetch the next feature from the stream.

$featureIO->write_feature($feature [,$another_feature,...])

Write the specified feature(s) to the stream.

TIEHANDLE(), READLINE(), PRINT()

These provide the tie interface. See perltie for more details.

FEEDBACK

Mailing Lists

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
http://bioperl.org/wiki/Mailing_lists  - About the mailing lists

Reporting Bugs

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.open-bio.org/

AUTHOR - Allen Day

Email allenday@ucla.edu

APPENDIX

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

new

Title   : new
Usage   : $stream = Bio::FeatureIO->new(-file => $filename, -format => 'Format')
Function: Returns a new feature stream
Returns : A Bio::FeatureIO stream initialised with the appropriate format
Args    : Named parameters:
            -file => $filename
            -fh => filehandle to attach to
            -format => format

newFh

Title   : newFh
Usage   : $fh = Bio::FeatureIO->newFh(-file=>$filename,-format=>'Format')
Function: does a new() followed by an fh()
Example : $fh = Bio::FeatureIO->newFh(-file=>$filename,-format=>'Format')
          $feature = <$fh>;   # read a feature object
          print $fh $feature; # write a feature object
Returns : filehandle tied to the Bio::FeatureIO::Fh class
Args    :

See Bio::FeatureIO::Fh

fh

Title   : fh
Usage   : $obj->fh
Function:
Example : $fh = $obj->fh;      # make a tied filehandle
          $feature = <$fh>;   # read a feature object
          print $fh $feature; # write a feature object
Returns : filehandle tied to Bio::FeatureIO class
Args    : none

next_feature

Title   : next_feature
Usage   : $feature = stream->next_feature
Function: Reads the next feature object from the stream and returns it.

          Certain driver modules may encounter entries in the stream
          that are either misformatted or that use syntax not yet
          understood by the driver. If such an incident is
          recoverable, e.g., by dismissing a feature of a feature
          table or some other non-mandatory part of an entry, the
          driver will issue a warning. In the case of a
          non-recoverable situation an exception will be thrown.  Do
          not assume that you can resume parsing the same stream
          after catching the exception. Note that you can always turn
          recoverable errors into exceptions by calling
          $stream->verbose(2).

Returns : a Bio::SeqFeatureI feature object
Args    : none

See Bio::Root::RootI, Bio::SeqFeatureI

write_feature

Title   : write_feature
Usage   : $stream->write_feature($feature)
Function: writes the $feature object into the stream
Returns : 1 for success and 0 for error
Args    : Bio::SeqFeature object

_load_format_module

Title   : _load_format_module
Usage   : *INTERNAL FeatureIO stuff*
Function: Loads up (like use) a module at run time on demand
Example :
Returns :
Args    :

seq

Title   : seq
Usage   : $obj->seq() OR $obj->seq($newSeq)
Example :
Returns : Bio::SeqI object
Args    : newSeq (optional)

_filehandle

Title   : _filehandle
Usage   : $obj->_filehandle($newval)
Function: This method is deprecated. Call _fh() instead.
Example :
Returns : value of _filehandle
Args    : newvalue (optional)

_guess_format

Title   : _guess_format
Usage   : $obj->_guess_format($filename)
Function: guess format based on file suffix
Example :
Returns : guessed format of filename (lower case)
Args    :
Notes   : See "SUPPORTED FORMATS"