Bio::Structure::IO(3) Handler for Structure Formats


use Bio::Structure::IO;
$in = Bio::Structure::IO->new(-file => "inputfilename",
-format => 'pdb');
while ( my $struc = $in->next_structure() ) {
print "Structure ", $struc->id, " number of models: ",
scalar $struc->model,"\n";


Bio::Structure::IO is a handler module for the formats in the Structure::IO set (e.g. Bio::Structure::IO::pdb). It is the officially sanctioned way of getting at the format objects, which most people should use.

The Bio::Structure::IO system can be thought of like biological file handles. They are attached to filehandles with smart formatting rules (e.g. PDB format) and can either read or write structure objects (Bio::Structure objects, or more correctly, Bio::Structure::StructureI implementing objects, of which Bio::Structure is one such object). If you want to know what to do with a Bio::Structure object, read Bio::Structure.

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 Structure::IO object instance is configured for either input or output. A specific example of a stream object is the Bio::Structure::IO::pdb object.

Each stream object has functions





   $stream->type() # returns 'INPUT' or 'OUTPUT'

As an added bonus, you can recover a filehandle that is tied to the Structure::IOIO object, allowing you to use the standard <> and print operations to read and write structure::IOuence objects:

    use Bio::Structure::IO;
    $stream = Bio::Structure::IO->newFh(-format => 'pdb'); # read from standard input
    while ( $structure = <$stream> ) {
        # do something with $structure


    print $stream $structure; # when stream is in output mode



   $stream = Bio::Structure::IO->new(-file => 'filename',   -format=>$format);
   $stream = Bio::Structure::IO->new(-fh   => \*FILEHANDLE, -format=>$format);
   $stream = Bio::Structure::IO->new(-format => $format);

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

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

   $strucIO = Bio::Structure::IO->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.

Specify the format of the file. Supported formats include:

   pdb         Protein Data Bank format

If no format is specified and a filename is given, then the module will attempt to deduce it from the filename. If this is unsuccessful, PDB format is assumed.

The format name is case insensitive. 'PDB', 'Pdb' and 'pdb' are all supported.


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

This constructor behaves like new(), but returns a tied filehandle rather than a Bio::Structure::IO object. You can read structures 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 structure objects into an array like this:

  @structures = <$fh>;

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


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

$structure = $structIO->next_structure()

Fetch the next structure from the stream.

$structIO->write_structure($struc [,$another_struc,...])

Write the specified structure(s) to the stream.


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


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.

  [email protected]                  - General discussion  - About the mailing lists


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

[email protected]

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:

AUTHORS - Ewan Birney, Lincoln Stein, Kris Boulez

Email [email protected], [email protected], [email protected]


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


 Title   : new
 Usage   : $stream = Bio::Structure::IO->new(-file => $filename, -format => 'Format')
 Function: Returns a new structIOstream
 Returns : A Bio::Structure::IO handler initialised with the appropriate format
 Args    : -file => $filename
           -format => format
           -fh => filehandle to attach to


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


 Title   : fh
 Usage   : $obj->fh
 Example : $fh = $obj->fh;      # make a tied filehandle
           $structure = <$fh>;   # read a structure object
           print $fh $structure; # write a structure object
 Returns : filehandle tied to the Bio::Structure::IO::Fh class
 Args    :


 Title   : format
 Usage   : $format = $obj->format()
 Function: Get the structure format
 Returns : structure format
 Args    : none


 Title   : next_structure
 Usage   : $structure = stream->next_structure
 Function: Reads the next structure object from the stream and returns a
           Bio::Structure::Entry object.
           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) (see
           Bio::RootI POD page).
 Returns : a Bio::Structure::Entry object
 Args    : none


 Title   : write_structure
 Usage   : $stream->write_structure($structure)
 Function: writes the $structure object into the stream
 Returns : 1 for success and 0 for error
 Args    : Bio::Structure object


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


 Title   : _concatenate_lines
 Usage   : $s = _concatenate_lines($line, $continuation_line)
 Function: Private. Concatenates two strings assuming that the second stems
           from a continuation line of the first. Adds a space between both
           unless the first ends with a dash.
           Takes care of either arg being empty.
 Example :
 Returns : A string.
 Args    :


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


 Title   : _guess_format
 Usage   : $obj->_guess_format($filename)
 Example :
 Returns : guessed format of filename (lower case)
 Args    :