What is the Difference Between is and == in Python?
It’s really confusing for Python programmer. When to use ‘is’? When to use ‘==’? And what is the Difference Between is and == in Python?
Before getting into the difference here is quick syntax, you might be aware of.
A syntax for “is” expression:
a is b
A Syntax for “==” (equals) expression:
a == b
Note: Where ‘a’ and ‘b’ are two different Python objects.
If we consider it as a native language, both expression seems to be doing the same work. But does not hold true for Python.
So to find the difference between them, let’s make it simple. I will give you quick demonstration by using ”is” and “==” expressions with Python list.
Difference Between is and == in Python | “is” vs “==”
- The “is” expressions in Python evaluates and returns to True if two variables point to the same Python data object.
- The “==” expression holds True if the objects referred to by the variables are equal.
Without getting heedless, let’s take the example of using “is” and “==” on the Python list.
“is” expression with List object:
a = [1, 2, 3] b = a a is b #True c = list(a) a is c #False
So are you surprised by the output?
- When you use “b = a”, it does not create a new list. In fact, it creates a pointer pointing to the same list. As ‘a’ and ‘b’ points to the same list, ‘is’ expression returns True.
- When you use “c = list(a)”, it copies all the list values from list ‘a’ and creates a new list object. Now list ‘a’ and ‘c’ have the same data but occupies a different memory location. As ‘a’ and ‘c’ are two different lists, ‘is’ expression returns False.
Then how “==” (equals) is different from “is”?
“==” expression with List object:
a = [1, 2, 3] b = a a == b #True c = list(a) a == c #True
- As told above, expression “b = a” does not create a new list so the content will be the same pointed by two different list object. So it will return True if you do “a == b”.
- “c = list(a)” creates new list but both the list carries same data contents. So “a == c” evaluates to True.
Related read to explore Python List:
This is all about Difference Between is and == in Python. I know its little confusing. If you have any comment, feel free to write below.