# reference data type
class Demo:
 def __init__(self, name):
  self.name = name
demo = Demo('Demo')

# primitive type
foo = 1

from base import *
def read():
    print 'reference data id: ' + str(id(demo))
    print 'reference data value : ' + demo.name

    print 'primitive data id: ' + str(id(foo))
    print 'primitive data value: ' + str(foo)

import base

def write():
 print "\nOriginal:"
 print "Original reference data id: " + str(id(base.demo))
 base.demo.name = "Updated Demo" # this will reflect that change
 #base.demo = base.Demo("Updated Demo") # this won't relfect the change
 print "Original data id: " + str(id(base.foo))
 base.foo = 1000
 print "Original data id after assignment: " + str(id(base.foo))

import read
import write

print "before write"
read.read()

write.write()

print "\nafter write"
read.read()

In [1]: a = 10

In [2]: id(a)
Out[2]: 20429204

In [3]: a = 100

In [4]: id(a)
Out[4]: 20430108