Viewing file:  basic.py (4.8 KB) -rw-r--r--
Select action/file-type:
 (+) |  (+) |  (+) | Code (+) | Session (+) |  (+) | SDB (+) |  (+) |  (+) |  (+) |  (+) |  (+) |
'''
An introduction to 4RDF
If you want to use lower-level APIs, e.g. to create an empty model,
see schema.py
'''
'''
Note: if you get an exception such as
_pg.error: FATAL 1: user "root" does not exist
Then you may have to change the lines
from Ft.Rdf.Drivers import Postgres
#Create the database
connect = 'pygres_demo'
Postgres.CreateDb(connect)
Demo('Postgres', connect, 'pygres_demo')
to something like
from Ft.Rdf.Drivers import Postgres
#Create the database
connect = 'postgres@localhost:5432:pygres_demo'
Postgres.CreateDb(connect)
Demo('Postgres', connect, 'pygres_demo')
'''
import sys
from Ft.Lib import Uri
from Ft.Rdf import Util
from Ft.Rdf.RdfsHandler import RdfsConstraintViolation
from Ft.Xml.Domlette import NonvalidatingReader, PrettyPrint
def Demo(model, db):
#Print triples serialized from the document
print model.complete(None, None, None)
#Change the language to french
from Ft.Rdf import Statement
#First check the status
print model.complete('http://www.dlib.org', 'http://purl.org/metadata/dublin_core#Language', None)
ns = Statement.Statement('http://www.dlib.org', 'http://purl.org/metadata/dublin_core#Language', 'en')
model.remove(ns)
#Check again
print model.complete('http://www.dlib.org', 'http://purl.org/metadata/dublin_core#Language', None)
ns = Statement.Statement('http://www.dlib.org', 'http://purl.org/metadata/dublin_core#Language', 'fr')
model.add(ns)
#Check again
print model.complete('http://www.dlib.org', 'http://purl.org/metadata/dublin_core#Language', None)
#Now write it all back out in XML
from Ft.Rdf.Serializers.Dom import Serializer
serializer = Serializer()
outdoc = serializer.serialize(model)
PrettyPrint(outdoc)
db.commit()
return
def MemorySetup():
#With the memory driver, the model is not persistent
from Ft.Rdf.Drivers import Memory
#Note that the name is not significant for the memory driver
uri = Uri.OsPathToUri('w3c1.rdf', attemptAbsolute=True)
model, db = Util.DeserializeFromUri(uri, driver=Memory,
dbName='memory_demo', create=True)
return model, db
#Dbm driver for simple persistence
def DbmSetup():
from Ft.Rdf.Drivers import Dbm
#The dbm database name is the name of the DB or DBM file
#if not Dbm.ExistsDb('mydemo.dbm'):
# db = Dbm.CreateDb('mydemo.dbm')
#else:
# db = Dbm.GetDb('mydemo.dbm')
#db.begin()
uri = Uri.OsPathToUri('w3c1.rdf', attemptAbsolute=True)
model, db = Util.DeserializeFromUri(uri, driver=Dbm,
dbName='dbm_demo', create=True)
return model, db
def SqlSetup(driver, connect, modelName):
try:
driver = "Ft.Rdf.Drivers." + driver
driver_mod = __import__(driver, {}, {}, ["*"])
except:
raise SystemExit("Unknown driver '%s'" % driver)
uri = Uri.OsPathToUri('w3c1.rdf', attemptAbsolute=True)
model, db = Util.DeserializeFromUri(uri, driver=driver_mod,
dbName=connect, create=1)
#Set up to use the Postgres database of the given instance name
#db = driver_mod.GetDb(connect)
return model, db
if __name__ == '__main__':
print "Running the demo using the memory driver"
print "========================================"
model, db = MemorySetup()
Demo(model, db)
print "Demo completed.\n"
print "Running the demo using the Dbm driver"
print "====================================="
model, db = DbmSetup()
Demo(model, db)
print "Demo completed.\n"
## try:
## print "Attempt to run the demo using the PsycoPG driver"
## from Ft.Rdf.Drivers import Psyco
## #Create the database
## Psyco.CreateDb('dbname=ftrdf_demo', 'demo')
## Demo('Psyco', 'dbname=ftrdf_demo', 'demo')
## print "Demo completed\n"
## except:
## print "Psyco demo could not be completed.\n"
## sys.exit(0)
print "Attempting to run the demo using the Postgres driver"
print "===================================================="
try:
import _pg # so we can refer to _pg.error below
from Ft.Rdf.Drivers import Postgres
except:
print "Postgres demo could not be completed; PyGreSQL apparently not installed."
else:
try:
#Create the database
connect = 'pygres_demo'
#connect = 'rdf:postgres@localhost:5432:pygres_demo'
#Postgres.CreateDb(connect)
model, db = SqlSetup('Postgres', connect, 'pygres_demo')
Demo(model, db)
print "Demo completed.\n"
except (Exception, _pg.error), e:
print "Postgres demo could not be completed. Reason:\n"
print e
print "\nEnd of tests."
|