#!/usr/bin/python

# Filename : python_dictionary.py

#A Python dictionary is a collection which contains key value pairs, where the

#key must be an immutable object

def print_dict(the_dict, msg="Contents of the dict"):

print msg

for key, value in the_dict.items():

print key, value

pop = {'China' : 1337722000,

'India' : 1162210000,

'United States' : 306261000}

print 'The population of India is ', pop['India']

#We have 3 countried let's add 2 more

pop['Indonesia'] = 229976124

pop['Brazil'] = 191080000

print_dict(pop, 'The 5 highest populated countries in the world are (unsorted)')

#Let's say we decide to keep only top 3

del(pop['Indonesia'])

del(pop['Brazil'])

print_dict(pop, 'The 3 highest populated countries in the world are (unsorted)')

class SimpleMutableClass:

def __init__(self, num):

self.num = num

smc1 = SimpleMutableClass(4)

#maps can only have immutable objects as keys, we try putting a mutable object

illegal_dict = {smc1 : 4}

#We are able to create and print the map

print illegal_dict[smc1]

#Lets mutate the key

smc1.num = 6

#Mutation not reflected in the dict

assert illegal_dict[smc1] == 4

#But the change did happen

assert smc1.num == 6