id() function in Python

In Python, id() function is a built-in function that returns the unique identifier of an object. The identifier is an integer, which represents the memory address of the object. The id() function is commonly used to check if two variables or objects refer to the same memory location.

Python id() Function Syntax

Syntax: id(object)

Return: a unique integer for a given object

How id() Function Work?

In this example, we can see the function accepts a single parameter and is used to return the identity of an object. This identity has to be unique and constant for this object during its lifetime. Two objects with non-overlapping lifetimes may have the same id() value. If we relate this to C, they are the memory address, here in Python it is the unique ID. This function is generally used internally in Python. 

Python3

x = 42
y = x
z = 42

print(id(x))
print(id(y))  # (same as x)
print(id(z))  # (same as x and y)

Output

140642115230496
140642115230496
140642115230496

Python id() function Examples

Below are the ways with which we can use id() function in Python:

• Inbuilt DataTypes
• Custom Object
• With Sets
• With Tuples

Python id() for Inbuilt DataTypes

In this example, we are printing the id of multiple datatypes like strings and lists to get object identity in Python

Python3

# This program shows various identities
str1 = "geek"
print(id(str1))

str2 = "geek"
print(id(str2))

# This will return True
print(id(str1) == id(str2))

# Use in Lists
list1 = ["aakash", "priya", "abdul"]
print(id(list1[0]))
print(id(list1[2]))

# This returns false
print(id(list1[0])==id(list1[2]))

Output

140161148229168
140161148229168
True
140161147809712
140161147916400
False

Python id() for custom object

In this example, we are creating the Python class and we are creating two Python class objects and checking their ids to get object identity in Python.

Python3

class MyClass:
    pass

# Create two instances of MyClass
obj1 = MyClass()
obj2 = MyClass()

# Print the id of each object
print(id(obj1))
print(id(obj2))

Output

140225741483792
140225741483856

Python id() with Sets

In this example, we are using the id function on sets to get object identity in Python.

Python3

set1 = {1, 2, 3}
set2 = {3, 2, 1}
set3 = {1, 2, 3}

print(id(set1))  # Output: <id1>
print(id(set2))  # Output: <id2>
print(id(set3))  # Output: <id3>

Output

140483509094352
140483509093872
140483509095792

Python id() with Tuples

In this example, we are using the id function on tuples to get object identity in Python.

Python3

tuple1 = (1, 2, 3)
tuple2 = (3, 2, 1)
tuple3 = (1, 2, 3)

print(id(tuple1))  # Output: <id1>
print(id(tuple2))  # Output: <id2>
print(id(tuple3))  # Output: <id3>

Output

140544960491680
140544960107456
140544960491680