What is the difference between Python's equality operators?

Python provides two very similar equality operators used for comparisons:

• The double equals (==), also known as the equality operator
• The is keyword, also known as the identity operator

Although similar to one another, the double equals (==) and the is keyword are used for different comparison purposes and yield different results.

The main difference between the two is that the is keyword checks for reference equality while the double equals (==) operator checks for value equality. In other words, is will return True if two variables both refer to the same object in memory (aka. identity), whereas the double equals operator will evaluate to True if the two objects have the same value.

Here are some examples to clear up any confusion:

a = [1, 2, 3]
b = a
c = [x for x in a]

print([
  a == b, # True
  a is b, # True
  a == c, # True
  a is c  # False
])

x = 'hi'
y = x
z = 'HI'.lower()

print([
  x == y, # True
  x is y, # True
  x == z, # True
  x is z  # False
])

Image credit: cyril mazarin on Unsplash