External Representations of Block Designs#
The “ext_rep” module is an API to the abstract tree represented by an XML document containing the External Representation of a list of block designs. The module also provides the related I/O operations for reading/writing ext-rep files or data. The parsing is based on expat.
This is a modified form of the module ext_rep.py (version 0.8) written by Peter Dobcsanyi [Do2009] peter@designtheory.org.
Todo
The XML data from the designtheory.org database contains a wealth of information about things like automorphism groups, transitivity, cycle type representatives, etc, but none of this data is made available through the current implementation.
Functions#
- class sage.combinat.designs.ext_rep.XTree(node)#
Bases:
object
A lazy class to wrap a rooted tree representing an XML document. The tree’s nodes are tuples of the structure:
(name, {dictionary of attributes}, [list of children])
Methods and services of an XTree object
t
:t.attribute
– attribute namedt.child
– first child namedt[i]
– i-th childfor child in t:
– iterate overt
’s childrenlen(t)
– number oft
’s children
If child is not an empty subtree, return the subtree as an
XTree
object. If child is an empty subtree, return_name
of the subtree. Otherwise return the child itself.The lazy tree idea originated from a utility class of the pyRXP 0.9 package by Robin Becker at ReportLab.
- class sage.combinat.designs.ext_rep.XTreeProcessor#
Bases:
object
An incremental event-driven parser for ext-rep documents. The processing stages:
<list_of_designs ...>
opening element. call-back:list_of_designs_proc
<list_definition>
subtree. call-back:list_definition_proc
<info>
subtree. call-back:info_proc
iterating over
<designs>
processing each<block_design>
separately. call-back:block_design_proc
finishing with closing
</designs>
and</list_of_designs>
.
- parse(xml_source)#
The main parsing function. Given an XML source (either a file handle or a string), parse the entire XML source.
EXAMPLES:
sage: from sage.combinat.designs import ext_rep sage: file_loc = ext_rep.dump_to_tmpfile(ext_rep.v2_b2_k2_icgsa) sage: proc = ext_rep.XTreeProcessor() sage: proc.save_designs = True sage: f = ext_rep.open_extrep_file(file_loc) sage: proc.parse(f) sage: f.close() sage: os.remove(file_loc) sage: proc.list_of_designs[0] (2, [[0, 1], [0, 1]])
- sage.combinat.designs.ext_rep.check_dtrs_protocols(input_name, input_pv)#
Check that the XML data is in a valid format. We can currently handle version 2.0. For more information see http://designtheory.org/library/extrep/
EXAMPLES:
sage: from sage.combinat.designs import ext_rep sage: ext_rep.check_dtrs_protocols('source', '2.0') sage: ext_rep.check_dtrs_protocols('source', '3.0') Traceback (most recent call last): ... RuntimeError: Incompatible dtrs_protocols: program: 2.0 source: 3.0
- sage.combinat.designs.ext_rep.designs_from_XML(fname)#
Return a list of designs contained in an XML file fname. The list contains tuples of the form (v, bs) where v is the number of points of the design and bs is the list of blocks.
EXAMPLES:
sage: from sage.combinat.designs import ext_rep sage: file_loc = ext_rep.dump_to_tmpfile(ext_rep.v2_b2_k2_icgsa) sage: ext_rep.designs_from_XML(file_loc)[0] (2, [[0, 1], [0, 1]]) sage: os.remove(file_loc) sage: from sage.combinat.designs import ext_rep sage: from sage.combinat.designs.block_design import BlockDesign sage: file_loc = ext_rep.dump_to_tmpfile(ext_rep.v2_b2_k2_icgsa) sage: v, blocks = ext_rep.designs_from_XML(file_loc)[0] sage: d = BlockDesign(v, blocks) sage: d.blocks() [[0, 1], [0, 1]] sage: d.is_t_design(t=2) True sage: d.is_t_design(return_parameters=True) (True, (2, 2, 2, 2))
- sage.combinat.designs.ext_rep.designs_from_XML_url(url)#
Return a list of designs contained in an XML file named by a URL. The list contains tuples of the form (v, bs) where v is the number of points of the design and bs is the list of blocks.
EXAMPLES:
sage: from sage.combinat.designs import ext_rep sage: file_loc = ext_rep.dump_to_tmpfile(ext_rep.v2_b2_k2_icgsa) sage: ext_rep.designs_from_XML_url("file://" + file_loc)[0] (2, [[0, 1], [0, 1]]) sage: os.remove(file_loc) sage: from sage.combinat.designs import ext_rep sage: ext_rep.designs_from_XML_url("http://designtheory.org/database/v-b-k/v3-b6-k2.icgsa.txt.bz2") # optional - internet [(3, [[0, 1], [0, 1], [0, 1], [0, 1], [0, 1], [0, 2]]), (3, [[0, 1], [0, 1], [0, 1], [0, 1], [0, 2], [0, 2]]), (3, [[0, 1], [0, 1], [0, 1], [0, 1], [0, 2], [1, 2]]), (3, [[0, 1], [0, 1], [0, 1], [0, 2], [0, 2], [0, 2]]), (3, [[0, 1], [0, 1], [0, 1], [0, 2], [0, 2], [1, 2]]), (3, [[0, 1], [0, 1], [0, 2], [0, 2], [1, 2], [1, 2]])]
- sage.combinat.designs.ext_rep.dump_to_tmpfile(s)#
Utility function to dump a string to a temporary file.
EXAMPLES:
sage: from sage.combinat.designs import ext_rep sage: file_loc = ext_rep.dump_to_tmpfile("boo") sage: os.remove(file_loc)
- sage.combinat.designs.ext_rep.open_extrep_file(fname)#
Try to guess the compression type from extension and open the extrep file.
EXAMPLES:
sage: from sage.combinat.designs import ext_rep sage: file_loc = ext_rep.dump_to_tmpfile(ext_rep.v2_b2_k2_icgsa) sage: proc = ext_rep.XTreeProcessor() sage: f = ext_rep.open_extrep_file(file_loc) sage: proc.parse(f) sage: f.close() sage: os.remove(file_loc)
- sage.combinat.designs.ext_rep.open_extrep_url(url)#
Try to guess the compression type from extension and open the extrep file pointed to by the url. This function (unlike open_extrep_file) returns the uncompressed text contained in the file.
EXAMPLES:
sage: from sage.combinat.designs import ext_rep sage: file_loc = ext_rep.dump_to_tmpfile(ext_rep.v2_b2_k2_icgsa) sage: proc = ext_rep.XTreeProcessor() sage: s = ext_rep.open_extrep_url("file://" + file_loc) sage: proc.parse(s) sage: os.remove(file_loc) sage: from sage.combinat.designs import ext_rep sage: s = ext_rep.designs_from_XML_url("http://designtheory.org/database/v-b-k/v3-b6-k2.icgsa.txt.bz2") # optional - internet