What is the difference between is and == in Python?
Antek N
In Python, theis operator and the== operator are used for different purposes and have different behaviors. Here's a detailed explanation of the differences betweenis and==:
is Operator:
Theis operator checks whether two variables or objects refer to the same memory location. It evaluates toTrue if the two operands are the same object, andFalse otherwise.
1
2
3
4
5
6
7
a = [1, 2, 3]
b = a
c = [1, 2, 3]
print(a is b) # Output: True
print(a is c) # Output: False
In this example,a andb refer to the same list object, soa is b evaluates toTrue. However,a andc are different list objects, even though they have the same values. Therefore,a is c evaluates toFalse.
It's important to note that theis operator checks for identity, comparing the memory addresses of the objects, rather than their values.
== Operator:
The== operator is used to check if two objects have the same value. It evaluates toTrue if the values of the two operands are equal, andFalse otherwise.
1
2
3
4
5
6
7
a = [1, 2, 3]
b = [1, 2, 3]
c = [1, 2, 3]
print(a == b) # Output: True
print(a == c) # Output: True
In this example,a andb have the same values, soa == b evaluates toTrue. Similarly,a andc have the same values, soa == c also evaluates toTrue.
Unlike theis operator, the== operator compares the values of the objects, not their memory addresses.
Differences betweenis and==:
The main differences betweenis and== are:
1. Comparison Type: Theis operator compares object identity, checking if two objects refer to the same memory location. The== operator compares object values, checking if the values of two objects are equal.
2. Usage: Theis operator is used to check if two objects are the same object. The== operator is used to check if two objects have the same value.
3. Behavior with Immutable Objects: For immutable objects like integers and strings,is and== may produce the same result, but it's not guaranteed. However, for mutable objects like lists,is and== can have different results.
4. Overriding: The== operator can be overridden by classes to define custom comparison behavior, whereas theis operator cannot be overridden.
In most cases, you should use the== operator to compare values, as it checks for equality based on the values of the objects. Theis operator should be used when you explicitly want to check if two variables or objects refer to the same memory location.
It's important to understand the distinction betweenis and== and use the appropriate operator based on the intended comparison.
