PythonReverseDict.py

class ReverseDict(object):
	""" Creates a reverse dictionary, and keeps the connection. Only key access works. """
	def __init__(self,dic):
		self.dic = dic
	def __getitem__(self,p):
		for k in self.dic:
			if self.dic[k] == p:
				return k
				
# here we have a simple dictionary		
d = {
	1: "apple",
	2: "pear"
}

# printing the values
print d[1]
print d[2]

# create a reverse dictionary
r = ReverseDict(d)

# we can fetch keys from values
print r["apple"]
print r["pear"]

# and if we update the dictionary, it still works
d.update({4:"banana"})
print r["banana"]