Array passing "by value" and "by reference" in Python

array_demo.py

# Demo of passing an array
# such that the original array
# is:
# 1. Changed
# 2. Remains unchanged

# Python 3

import copy
from array import array

def func(arr):
    print('Object Identifier: {0:d}'.format(id(arr)))
    for i in range(0,len(arr)):
        arr[i] = arr[i]**2

if __name__=='__main__':

    print('\nOriginal array changes::\n')
    arr=array('i',[1,2,3])
    print(arr)
    print('Object Identifier: {0:d}'.format(id(arr)))
    # results in passing a reference to the
    # the original array
    func(arr)
    print(arr)

    # send a copy
    print('\nOriginal array doesn\'t change::\n')
    arr=array('i',[1,2,3])
    print(arr)
    print('Object Identifier: {0:d}'.format(id(arr)))
    # Pass the copy of 
    # the original array
    myarr = copy.copy(arr)
    func(myarr)

    print(arr)

Sample output

Original array changes::

array('i', [1, 2, 3])
Object Identifier: 3075060736
Object Identifier: 3075060736
array('i', [1, 4, 9])

Original array doesn't change::

array('i', [1, 2, 3])
Object Identifier: 3075063072
Object Identifier: 3075060736
array('i', [1, 2, 3])