#!/usr/bin/env python

"""
   Parameters in Python are passed by value. 
   We need to have in mind the following:
    1- The parameter passed in is actually a reference to a 
       variable (but the reference is passed by value)
    2- Some data types are mutable, but others aren't
"""

# Example 1: List - a mutable type
#            Here we will a list is passed as argument of a function
#            modified inside using a mutable list methods.
#            There is a new value of the list outside the function.

def try_to_change_list_contents(the_list):
    print 'got', the_list
    the_list.append('four')
    print 'changed to', the_list

outer_list = ['one', 'two', 'three']

print 'before, outer_list =', outer_list
try_to_change_list_contents(outer_list)
print 'after, outer_list =', outer_list