Source code for rdflib.util

"""
Some utility functions.

Miscellaneous utilities

* list2set
* first
* uniq
* more_than

Term characterisation and generation

* to_term
* from_n3

Date/time utilities

* date_time
* parse_date_time

Statement and component type checkers

* check_context
* check_subject
* check_predicate
* check_object
* check_statement
* check_pattern

"""

from calendar import timegm
from time import altzone

# from time import daylight
from time import gmtime
from time import localtime
from time import time
from time import timezone

from os.path import splitext

from rdflib.exceptions import ContextTypeError
from rdflib.exceptions import ObjectTypeError
from rdflib.exceptions import PredicateTypeError
from rdflib.exceptions import SubjectTypeError
import rdflib.graph  # avoid circular dependency
from rdflib.namespace import Namespace
from rdflib.namespace import NamespaceManager
from rdflib.term import BNode
from rdflib.term import Literal
from rdflib.term import URIRef
from rdflib.compat import sign

__all__ = [
    "list2set",
    "first",
    "uniq",
    "more_than",
    "to_term",
    "from_n3",
    "date_time",
    "parse_date_time",
    "check_context",
    "check_subject",
    "check_predicate",
    "check_object",
    "check_statement",
    "check_pattern",
    "guess_format",
    "find_roots",
    "get_tree",
]


[docs]def list2set(seq): """ Return a new list without duplicates. Preserves the order, unlike set(seq) """ seen = set() return [x for x in seq if x not in seen and not seen.add(x)]
[docs]def first(seq): """ return the first element in a python sequence for graphs, use graph.value instead """ for result in seq: return result return None
[docs]def uniq(sequence, strip=0): """removes duplicate strings from the sequence.""" if strip: return set(s.strip() for s in sequence) else: return set(sequence)
[docs]def more_than(sequence, number): "Returns 1 if sequence has more items than number and 0 if not." i = 0 for item in sequence: i += 1 if i > number: return 1 return 0
[docs]def to_term(s, default=None): """ Creates and returns an Identifier of type corresponding to the pattern of the given positional argument string ``s``: '' returns the ``default`` keyword argument value or ``None`` '<s>' returns ``URIRef(s)`` (i.e. without angle brackets) '"s"' returns ``Literal(s)`` (i.e. without doublequotes) '_s' returns ``BNode(s)`` (i.e. without leading underscore) """ if not s: return default elif s.startswith("<") and s.endswith(">"): return URIRef(s[1:-1]) elif s.startswith('"') and s.endswith('"'): return Literal(s[1:-1]) elif s.startswith("_"): return BNode(s) else: msg = "Unrecognised term syntax: '%s'" % s raise Exception(msg)
[docs]def from_n3(s: str, default=None, backend=None, nsm=None): r''' Creates the Identifier corresponding to the given n3 string. >>> from_n3('<http://ex.com/foo>') == URIRef('http://ex.com/foo') True >>> from_n3('"foo"@de') == Literal('foo', lang='de') True >>> from_n3('"""multi\nline\nstring"""@en') == Literal( ... 'multi\nline\nstring', lang='en') True >>> from_n3('42') == Literal(42) True >>> from_n3(Literal(42).n3()) == Literal(42) True >>> from_n3('"42"^^xsd:integer') == Literal(42) True >>> from rdflib import RDFS >>> from_n3('rdfs:label') == RDFS['label'] True >>> nsm = NamespaceManager(rdflib.graph.Graph()) >>> nsm.bind('dbpedia', 'http://dbpedia.org/resource/') >>> berlin = URIRef('http://dbpedia.org/resource/Berlin') >>> from_n3('dbpedia:Berlin', nsm=nsm) == berlin True ''' if not s: return default if s.startswith("<"): # Hack: this should correctly handle strings with either native unicode # characters, or \u1234 unicode escapes. return URIRef(s[1:-1].encode("raw-unicode-escape").decode("unicode-escape")) elif s.startswith('"'): if s.startswith('"""'): quotes = '"""' else: quotes = '"' value, rest = s.rsplit(quotes, 1) value = value[len(quotes) :] # strip leading quotes datatype = None language = None # as a given datatype overrules lang-tag check for it first dtoffset = rest.rfind("^^") if dtoffset >= 0: # found a datatype # datatype has to come after lang-tag so ignore everything before # see: http://www.w3.org/TR/2011/WD-turtle-20110809/ # #prod-turtle2-RDFLiteral datatype = from_n3(rest[dtoffset + 2 :], default, backend, nsm) else: if rest.startswith("@"): language = rest[1:] # strip leading at sign value = value.replace(r"\"", '"') # unicode-escape interprets \xhh as an escape sequence, # but n3 does not define it as such. value = value.replace(r"\x", r"\\x") # Hack: this should correctly handle strings with either native unicode # characters, or \u1234 unicode escapes. value = value.encode("raw-unicode-escape").decode("unicode-escape") return Literal(value, language, datatype) elif s == "true" or s == "false": return Literal(s == "true") elif s.isdigit(): return Literal(int(s)) elif s.startswith("{"): identifier = from_n3(s[1:-1]) return rdflib.graph.QuotedGraph(backend, identifier) elif s.startswith("["): identifier = from_n3(s[1:-1]) return rdflib.graph.Graph(backend, identifier) elif s.startswith("_:"): return BNode(s[2:]) elif ":" in s: if nsm is None: # instantiate default NamespaceManager and rely on its defaults nsm = NamespaceManager(rdflib.graph.Graph()) prefix, last_part = s.split(":", 1) ns = dict(nsm.namespaces())[prefix] return Namespace(ns)[last_part] else: return BNode(s)
[docs]def check_context(c): if not (isinstance(c, URIRef) or isinstance(c, BNode)): raise ContextTypeError("%s:%s" % (c, type(c)))
[docs]def check_subject(s): """Test that s is a valid subject identifier.""" if not (isinstance(s, URIRef) or isinstance(s, BNode)): raise SubjectTypeError(s)
[docs]def check_predicate(p): """Test that p is a valid predicate identifier.""" if not isinstance(p, URIRef): raise PredicateTypeError(p)
[docs]def check_object(o): """Test that o is a valid object identifier.""" if not (isinstance(o, URIRef) or isinstance(o, Literal) or isinstance(o, BNode)): raise ObjectTypeError(o)
[docs]def check_statement(triple): (s, p, o) = triple if not (isinstance(s, URIRef) or isinstance(s, BNode)): raise SubjectTypeError(s) if not isinstance(p, URIRef): raise PredicateTypeError(p) if not (isinstance(o, URIRef) or isinstance(o, Literal) or isinstance(o, BNode)): raise ObjectTypeError(o)
[docs]def check_pattern(triple): (s, p, o) = triple if s and not (isinstance(s, URIRef) or isinstance(s, BNode)): raise SubjectTypeError(s) if p and not isinstance(p, URIRef): raise PredicateTypeError(p) if o and not ( isinstance(o, URIRef) or isinstance(o, Literal) or isinstance(o, BNode) ): raise ObjectTypeError(o)
[docs]def date_time(t=None, local_time_zone=False): """http://www.w3.org/TR/NOTE-datetime ex: 1997-07-16T19:20:30Z >>> date_time(1126482850) '2005-09-11T23:54:10Z' @@ this will change depending on where it is run #>>> date_time(1126482850, local_time_zone=True) #'2005-09-11T19:54:10-04:00' >>> date_time(1) '1970-01-01T00:00:01Z' >>> date_time(0) '1970-01-01T00:00:00Z' """ if t is None: t = time() if local_time_zone: time_tuple = localtime(t) if time_tuple[8]: tz_mins = altzone // 60 else: tz_mins = timezone // 60 tzd = "-%02d:%02d" % (tz_mins // 60, tz_mins % 60) else: time_tuple = gmtime(t) tzd = "Z" year, month, day, hh, mm, ss, wd, y, z = time_tuple s = "%0004d-%02d-%02dT%02d:%02d:%02d%s" % (year, month, day, hh, mm, ss, tzd) return s
[docs]def parse_date_time(val): """always returns seconds in UTC # tests are written like this to make any errors easier to understand >>> parse_date_time('2005-09-11T23:54:10Z') - 1126482850.0 0.0 >>> parse_date_time('2005-09-11T16:54:10-07:00') - 1126482850.0 0.0 >>> parse_date_time('1970-01-01T00:00:01Z') - 1.0 0.0 >>> parse_date_time('1970-01-01T00:00:00Z') - 0.0 0.0 >>> parse_date_time("2005-09-05T10:42:00") - 1125916920.0 0.0 """ if "T" not in val: val += "T00:00:00Z" ymd, time = val.split("T") hms, tz_str = time[0:8], time[8:] if not tz_str or tz_str == "Z": time = time[:-1] tz_offset = 0 else: signed_hrs = int(tz_str[:3]) mins = int(tz_str[4:6]) secs = (sign(signed_hrs) * mins + signed_hrs * 60) * 60 tz_offset = -secs year, month, day = ymd.split("-") hour, minute, second = hms.split(":") t = timegm( (int(year), int(month), int(day), int(hour), int(minute), int(second), 0, 0, 0) ) t = t + tz_offset return t
SUFFIX_FORMAT_MAP = { "xml": "xml", "rdf": "xml", "owl": "xml", "n3": "n3", "ttl": "turtle", "nt": "nt", "trix": "trix", "xhtml": "rdfa", "html": "rdfa", "svg": "rdfa", "nq": "nquads", "trig": "trig", "json": "json-ld", "jsonld": "json-ld", "json-ld": "json-ld", }
[docs]def guess_format(fpath, fmap=None): """ Guess RDF serialization based on file suffix. Uses ``SUFFIX_FORMAT_MAP`` unless ``fmap`` is provided. Examples: >>> guess_format('path/to/file.rdf') 'xml' >>> guess_format('path/to/file.owl') 'xml' >>> guess_format('path/to/file.ttl') 'turtle' >>> guess_format('path/to/file.json') 'json-ld' >>> guess_format('path/to/file.xhtml') 'rdfa' >>> guess_format('path/to/file.svg') 'rdfa' >>> guess_format('path/to/file.xhtml', {'xhtml': 'grddl'}) 'grddl' This also works with just the suffixes, with or without leading dot, and regardless of letter case:: >>> guess_format('.rdf') 'xml' >>> guess_format('rdf') 'xml' >>> guess_format('RDF') 'xml' """ fmap = fmap or SUFFIX_FORMAT_MAP return fmap.get(_get_ext(fpath)) or fmap.get(fpath.lower())
def _get_ext(fpath, lower=True): """ Gets the file extension from a file(path); stripped of leading '.' and in lower case. Examples: >>> _get_ext("path/to/file.txt") 'txt' >>> _get_ext("OTHER.PDF") 'pdf' >>> _get_ext("noext") '' >>> _get_ext(".rdf") 'rdf' """ ext = splitext(fpath)[-1] if ext == "" and fpath.startswith("."): ext = fpath if lower: ext = ext.lower() if ext.startswith("."): ext = ext[1:] return ext
[docs]def find_roots(graph, prop, roots=None): """ Find the roots in some sort of transitive hierarchy. find_roots(graph, rdflib.RDFS.subClassOf) will return a set of all roots of the sub-class hierarchy Assumes triple of the form (child, prop, parent), i.e. the direction of RDFS.subClassOf or SKOS.broader """ non_roots = set() if roots is None: roots = set() for x, y in graph.subject_objects(prop): non_roots.add(x) if x in roots: roots.remove(x) if y not in non_roots: roots.add(y) return roots
[docs]def get_tree( graph, root, prop, mapper=lambda x: x, sortkey=None, done=None, dir="down" ): """ Return a nested list/tuple structure representing the tree built by the transitive property given, starting from the root given i.e. get_tree(graph, rdflib.URIRef("http://xmlns.com/foaf/0.1/Person"), rdflib.RDFS.subClassOf) will return the structure for the subClassTree below person. dir='down' assumes triple of the form (child, prop, parent), i.e. the direction of RDFS.subClassOf or SKOS.broader Any other dir traverses in the other direction """ if done is None: done = set() if root in done: return done.add(root) tree = [] if dir == "down": branches = graph.subjects(prop, root) else: branches = graph.objects(root, prop) for branch in branches: t = get_tree(graph, branch, prop, mapper, sortkey, done, dir) if t: tree.append(t) return (mapper(root), sorted(tree, key=sortkey))
def test(): import doctest doctest.testmod() if __name__ == "__main__": # try to make the tests work outside of the time zone they were written in # import os, time # os.environ['TZ'] = 'US/Pacific' # try: # time.tzset() # except AttributeError, e: # print e # pass # tzset missing! see # http://mail.python.org/pipermail/python-dev/2003-April/034480.html test() # pragma: no cover