ligo.lw package

DOM-like library for handling LIGO Light Weight XML files. For more information on the Python DOM specification and SAX document content handlers, please refer to the Python standard library reference and the documentation it links to.

Here is a brief tutorial for a common use case: load a LIGO Light-Weight XML document containing tabular data complying with the LSC table definitions, access rows in the tables including the use of ID-based cross references, modify the contents of a table, and finally write the document back to disk. Please see the documentation for the modules, classes, functions, and methods shown below for more information.

Example:

>>> # import modules
>>> from ligo.lw import ligolw
>>> from ligo.lw import lsctables
>>> from ligo.lw import utils as ligolw_utils
>>>
>>> # define a content handler
>>> class LIGOLWContentHandler(ligolw.LIGOLWContentHandler):
...     pass
...
>>> lsctables.use_in(LIGOLWContentHandler)
>>>
>>> # load a document.  gzip'ed files are auto-detected
>>> filename = "demo.xml.gz"
>>> xmldoc = ligolw_utils.load_filename(filename, contenthandler = LIGOLWContentHandler, verbose = True)
>>> 
>>> # retrieve the process and sngl_inspiral tables.  these are list-like
>>> # objects of rows.  the row objects' attributes are the column names
>>> process_table = lsctables.ProcessTable.get_table(xmldoc)
>>> sngl_inspiral_table = lsctables.SnglInspiralTable.get_table(xmldoc)
>>> 
>>> # fix the mtotal column in the sngl_inspiral table
>>> for row in sngl_inspiral_table:
...     row.mtotal = row.mass1 + row.mass2
...
>>> # construct a look-up table mapping process_id to row in process table
>>> index = dict((row.process_id, row) for row in process_table)
>>> 
>>> # for each trigger in the sngl_inspiral table, print the name of the user
>>> # who ran the job that produced it, the computer on which the job ran, and
>>> # the GPS end time of the trigger
>>> for row in sngl_inspiral_table:
...     process = index[row.process_id]
...     print "%s@%s: %s s" % (process.username, process.node, str(row.get_end()))
...
>>> # write document.  must explicitly state whether or not the file is to be
>>> # gzip compressed
>>> ligolw_utils.write_filename(xmldoc, filename, gz = filename.endswith(".gz"), verbose = True)