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Bio::HandlerBaseI(3pm) User Contributed Perl Documentation Bio::HandlerBaseI(3pm)


Bio::HandlerBaseI - Interface class for handler methods which interact with any event-driven parsers (drivers).


  # MyHandler is a Bio::HandlerBaseI-derived class for dealing with GenBank
  # sequence data, derived from a GenBank event-driven parser
  # inside a parser (driver) constructor
  $self->seqhandler($handler || MyHandler->new(-format => 'genbank'));
  # in the driver parsing method ( such as next_seq() ) ...
  $handler = $self->seqhandler();
  # roll data up into hashref chunks, pass off into Handler for processing...
  # or retrieve Handler methods and pass data directly to Handler methods
  my $hmeth = $hobj->handler_methods;
  if ($hmeth->{ $data->{NAME} }) {
      my $mth = $hmeth->{ $data->{NAME} }; # code ref


This interface describes simple class methods used for processing data from an event-based parser (a driver). This is similar in theme to an XML SAX-based driver but differs in that one can optionally pass related data semi-intelligently as chunks (defined in a hash reference) vs. passing as single data elements in a stream. For instance, any reference-related and species-related data as well as individual sequence features could be passed as chunks of data to be processed in part or as a whole (from Data::Dumper output):

Annotation Data (References):

  $VAR1 = {
          'NAME' => 'REFERENCE',
          'DATA' => '1  (bases 1 to 10001)'
          'AUTHORS' => 'International Human Genome Sequencing Consortium.'
          'TITLE' => 'The DNA sequence of Homo sapiens'
          'JOURNAL' => 'Unpublished (2003)'

Sequence features (source seqfeature):

  $VAR1 = {
          'mol_type' => 'genomic DNA',
          'LOCATION' => '<1..>10001',
          'NAME' => 'FEATURES',
          'FEATURE_KEY' => 'source',
          'note' => 'Accession AL451081 sequenced by The Sanger Centre',
          'db_xref' => 'taxon:9606',
          'clone' => 'RP11-302I18',
          'organism' => 'Homo sapiens'

These would be 'handled' accordingly by methods specified in a HandlerI-based class. The data in a chunk is intentionally left vague here since this may vary from implementation to implementation and can be somewhat open to interpretation. A data chunk in a sequence record, for instance, will be different than a data chunk in a BLAST report. This also allows one the flexibility to pass data as more XML-like small bits, as huge chunks, or even as indexed locations in a file (such as when using a "pull" parser, like a Bio::PullParserI).

For an sequence-based implementation see Bio::SeqIO::RichSeq::GenericRichSeqHandler, which handles any GenBank, UniProt, and EMBL data from their respective driver modules (Bio::SeqIO::gbdriver, Bio::SeqIO::swissdriver, and Bio::SeqIO::embldriver).


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.                  - General discussion  - About the mailing lists


Please direct usage questions or support issues to the mailing list:

rather than to the module maintainer directly. Many experienced and reponsive experts will be able look at the problem and quickly address it. Please include a thorough description of the problem with code and data examples if at all possible.

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:

AUTHOR - Chris Fields

Email cjfields at bioperl dot org


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


 Title   :  data_handler
 Usage   :  $handler->data_handler($data)
 Function:  Centralized method which accepts all data chunks, then distributes
            to the appropriate methods for processing based on the chunk name
            from within the HandlerBaseI object.
            One can also use
 Returns :  None
 Args    :  an hash ref containing a data chunk.


 Title   :  handler_methods
 Usage   :  $handler->handler_methods('GenBank')
            %handlers = $handler->handler_methods();
 Function:  Retrieve the handler methods used for the current format() in
            the handler.  This assumes the handler methods are already
            described in the HandlerI-implementing class.
 Returns :  a hash reference with the data type handled and the code ref
            associated with it.
 Args    :  [optional] String representing the sequence format.  If set here
            this will also set sequence_format()
 Throws  :  On unimplemented sequence format in %HANDLERS


 Title   :  format
 Usage   :  $handler->format('GenBank')
 Function:  Get/Set the format for the report/record being parsed. This can be
            used to set handlers in classes which are capable of processing
            similar data chunks from multiple driver modules.
 Returns :  String with the sequence format
 Args    :  [optional] String with the sequence format
 Note    :  The format may be used to set the handlers (as in the
            current GenericRichSeqHandler implementation)


 Title   :  get_params
 Usage   :  $handler->get_params('-species')
 Function:  Convenience method used to retrieve the specified
            parameters from the internal parameter cache
 Returns :  Hash ref containing parameters requested and data as
            key-value pairs.  Note that some parameter values may be
            objects, arrays, etc.
 Args    :  List (array) representing the parameters requested


 Title   :  set_params
 Usage   :  $handler->set_params({
                                '-species' => $species,
                                '-accession_number' => $acc
 Function:  Convenience method used to set specific parameters
 Returns :  None
 Args    :  Hash ref containing the data to be passed as key-value pairs


 Title   :  reset_parameters
 Usage   :  $handler->reset_parameters()
 Function:  Resets the internal cache of data (normally object parameters for
            a builder or factory)
 Returns :  None
 Args    :  None
2021-08-15 perl v5.32.1