is

The is keyword is used to determine if two variables reference the same object.

Example

Python
a = 1
b = 1

if (a is b):
    print("a is b")
else:
    print('a is not b')

Output

a is b

Do not use the is operator to determine of the value of two objects are equal.  Use the == operator instead.

Example

Python
array1 = [1, 2, 3]
array2 = [1, 2, 3]
myArray = array1

if array1 is array2:
    print('array1 is array2')
else:
    print('array1 is NOT array2')

if array1 == array2:
    print('array 1 equals array 2')

if myArray is array1:
    print('myArray is array1')

Output

array1 is NOT array2
array 1 equals array 2
myArray is array1