Python Implementation of RAX
April 26, 2000
"""
RAX = Record API for XML
A simple, record-oriented API for XML. Provides a simple, efficient
interface for processing the sort of XML often generated from
databases
Sean McGrath
http://www.digitome.com
"""
import os,sys,string
class Record:
"""
A record drawn from an XML file is a collection of
elements accessed by element type name
"""
def __init__(self,ElementTypeName):
self.ElementTypeName = ElementTypeName
self.ElementStack = []
self.Elements = {}
self.CurrentChild = None
self.StartChild (ElementTypeName)
def GetField(self,ElementTypeName):
return self.Elements[ElementTypeName]
def StartChild(self,ElementTypeName):
"""
Start accumulating data for a new child element
"""
self.ElementStack.append (self.CurrentChild)
self.Elements[ElementTypeName] = ""
self.CurrentChild = ElementTypeName
def EndChild(self,ElementTypeName):
"""
End accumulating data for child element.
Subsequent content will be associated with enclosing element
"""
self.CurrentChild = self.ElementStack.pop()
def AddData(self,Data):
"""
Associate data with currently active element
"""
Data = string.strip (string.replace (Data,"\\n",""))
self.Elements[self.CurrentChild] = self.Elements[self.CurrentChild] + Data
class RAX:
"""
Record API for XML - base class
"""
def __init__(self,fo):
# Store file object from which ESIS is read
self.fo = fo
# Default "record" element
self.RecordElementTypeName = ""
def SetRecord(self,ElementTypeName):
"""
Set the "record" element
"""
self.RecordElementTypeName = ElementTypeName
def ReadRecord(self):
"""
Read a record.
"""
# Skip forward to the required start-tag event
line = self.fo.readline()[:-1]
while line and line[1:] != self.RecordElementTypeName:
line = self.fo.readline()[:-1]
if not line:
return None
# Create a new record
R = Record(line[1:])
# Trundle through accumulating info in the Record
# until the end-tag event occurs
line = self.fo.readline()[:-1]
while line and line[1:] != self.RecordElementTypeName:
if line[0] == "-":
if len(line)>1:
R.AddData(line[1:])
elif line[0] == "(":
R.StartChild(line[1:])
elif line[0] == ")":
R.EndChild(line[1:])
else:
sys.stderr.write ("Unsupported Event '%s'" % line[0])
line = self.fo.readline()[:-1]
return R
def test():
"""
Test function for RAX
Process customers.xml outputting various elements
"""
# This code trundles through the invoices, printing
# out the "from" and "to" elements.
fo = os.popen ("xmln customers.xml")
R = RAX(fo)
R.SetRecord("Record")
rec = R.ReadRecord()
while rec:
print "Phone=%s" % rec.GetField("Phone")
rec = R.ReadRecord()
if __name__ == "__main__":
test()