Python id()

Summary: in this tutorial, you’ll learn how to use the Python id() function to get the identity of an object.

Introduction to the Python id() function

The id() function accepts an object and returns an integer that identifies that object:

id(object)Code language: Python (python)

The returned integer is unique and doesn’t change during the lifetime of the object.

In Python, everything is an object including a number, a string, etc. For example:

x = 10
print(id(x))  # 2523002569232Code language: Python (python)

In this example, we define a variable x and set it to 10. Internally, Python creates a new integer object and references x to that object in the memory.

The id(x) returns an integer (2523002569232) that is corresponding to the memory address of the object that x references.

Note that you’ll see a different integer number every time you run the program.

To convert the memory address from an integer to hexadecimal, you use the hex() function:

x = 10
print(id(x))  # 2304409666064
print(hex(id(x)))  # 0x24b6eac0210Code language: Python (python)

The following defines two variables x and y and assigns 10 to both:

x = 10
y = 10
print(id(x) == id(y))  # TrueCode language: Python (python)

In this case, Python creates only one integer object with the value of 10 and references both the x and y variables to it. Therefore, the identity of the object that x and y reference is the same:

Python does the same way for string objects. For example:

a = 'Python'
b = 'Python'
print(id(a) == id(b))  # TrueCode language: Python (python)

Summary

• Use the id() function to get an integer, which is an identity of an object.