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.