Java like Property object written in Python - properties.py

I've been learning the python scripting language recently and decided to knock up a small script to kick off a daemon on my linux box.
I quickly got the script working, but it had a lot of hard coded values in it. I decided that I should use a properties file to initialise all those hard coded values as variables.
I wanted an object that behaved like the Java Property object that could be initialised from a property file and then queried in my script.
After a few days searching for such a thing I admitted defeat and decided to write my own, I was learning the language anyway so this could only help.

Python has a Map/Dictionary type object called a dictionary that you can create using the built-in function "dict()" I decided to extend it to have methods similar to Java's Properties object.

The following module - properties.py can be imported into a script and the Property object used to read a property file that ignors blank lines, lines begining with a "#" and leading white space on property names and values.

Properties are defined as "key value" pairs with the key and value being seperated with a ":" or a "=" character. A valid property file could look like:

# /var/tmp/testPropFile.properties file
# This is a sample
    #      properties file. lines
# begining with '#' are comments white space is ignored

propertyName1=value1
   propertyName2        =       value2
propertyName3 : value3

# this is a comment
   #so is this
propertyName4:value4

The Property object could be used in a script like this:

#!/usr/bin/python
#
# test the properties.py module
#
from properties import Property

props = Property()
props.loadProperties("/var/tmp/testPropFile.properties")

for n, v in props.iteritems():
	print n, " : ", v

print "the value of property propertyName3 is", props.getProperty("propertyName3")

props.setproperty("newKey","newkeyValue")

props.store("/var/tmp/testpropertyFile2.properties", "This is a test comment");
print "the value of name2 is ", props.getProperty("name2")
print "the value of newKeyis ", props.getProperty("newKey")

So here is my properties.py

#!/usr/bin/python
# Author: Karl Roberts
#
# python implementation of a Java Property object
#
# This file is in the public domain
# please feel free to use and edit it
# If you improove it please post a comment showing me how and I'll probably add
# it to this demo. cheers
#
import sys, os, string, re

class Property(dict):

	#dict of properties
	nvseppattern = re.compile("=|:")
	__commentre = re.compile("^\s*#|^\s*\n")

	def __init__(self,properties=None):
	"constructor. can be created by passing in another properties object if you want"
		if properties is not None:
			self.update(properties) 

	def getProperty(self, key):
		"Searches for the property with the specified key in this property list."
		return self[key]

	def list(self,out):
		"Prints this property list out to the specified output stream. This method is useful for debugging."
		return self.items()

	def loadProperties(self,propsFileName):
		"Reads a property list (key and element pairs) from the properties file"
		#read the properties file defined in init
		f = file(propsFileName)
		pList = f.readlines()
		#populate the dict with key value pairs (readline split on = or :
		# need to strip the keys and values & remove \n
		#wanted to do this with a generator majic but not got version 4 of python yet
		#so do it with a loop.
		i=0
		l=len(pList)
		while i < l:
			if re.match(self.__commentre,pList[i]):
				del(pList[i])
				l=len(pList)
				continue
			i=i+1
  
		mydic=dict([(l[0].strip(),l[1].strip()) for l in ([re.split(self.__nvseppattern,s,1) for s in pList])])
		self.update(mydic)
		return self

	def propertyNames(self):
		"Returns an iterator of all the keys in this property list, including distinct keys in the default property list if a key of the same name has not already been found from the main properties list."
		return self.iterkeys()

	def setProperty(self, key, value):
		"add a property to this object"
		self.update({key: value})

	def store(self, outputFileName, comment):
		"Outputs the properties to a file in a manner that can be read with load(). comment is a comment added to the top of the file"
		f = file(outputFileName, 'w+')
		f.write("# "+comment+"\n");
		for key, value in self.iteritems():
			f.write(key+"="+value + "\n")
		f.close()

#END of  File

Cheers