is not and != in Python

When comparing two values in Python, there are multiple operators that can be used, including is not and !=. Although they might seem similar, they serve different purposes and have different behaviors.

is not operator

The is not operator is used to test whether two objects are not equal by identity. In other words, it tests if the objects being compared are the same object in memory. This means that if two objects have different memory addresses, the is not operator will return True, even if their contents are the same.

a = [1, 2, 3]
b = [1, 2, 3]
print(a is not b)  # True, because a and b are two different objects in memory

!= operator

On the other hand, the != operator checks whether two objects are not equal by value. This means that it tests if the contents of the objects being compared are the same, regardless of their memory addresses. This operator is commonly used with string and numerical values.

x = 10
y = 9
print(x != y)  # True, because x and y have different values

Conclusion

In summary, the is not operator tests for object identity, while the != operator tests for value inequality. It is important to choose the appropriate operator based on the desired comparison behavior in your code.