Python hash() Built in Function

Python hash() is a built-in function that returns the hash value of an object if it has one. A hash value is an integer that represents the identity of an object and can be used to compare objects for equality or to store them in a dictionary or a set.

Here are some examples of how to use Python hash():

To get the hash value of different types of objects:

print(hash(181)) # returns 181
print(hash(181.23)) # returns 530343892119126197
print(hash("Python")) # returns 2230730083538390373 

To get the hash value of a user-defined class:

class Person:
    def __init__(self, name, age):
        self.name = name
        self.age = age

    def __hash__(self):
        return hash((self.name, self.age))

person1 = Person("John", 36)
person2 = Person("Mary", 28)
print(hash(person1)) # returns -9209083346939511628
print(hash(person2)) # returns -9209083346939511628

To use the hash value to check for object equality or membership:

class Person:
    def __init__(self, name, age):
        self.name = name
        self.age = age

    def __hash__(self):
        return hash((self.name, self.age))

    def __eq__(self, other):
        return (self.name, self.age) == (other.name, other.age)

person1 = Person("John", 36)
person2 = Person("Mary", 28)
person3 = Person("John", 36)

print(person1 == person3) # returns True
print(person2 == person3) # returns False

people = {person1, person2}
print(person3 in people) # returns True

If you have any questions about this code, you can drop a line in comment.

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