Python Built-in Methods – Python id() Function

Python id() Function

Returns a unique id of an object


The id() function returns a unique id for the specified object.



Parameter Condition Description
object Required Any object (such as number, string, list, class etc.)

What is ID of an Object?

In Python, every object has its own unique id. Every time you create an object, a unique id is assigned to it.

The id is nothing but the address of the object in memory. So, it will be different for each time you run the program.

Basic Examples

Use id() function to get a unique id of the object.

x = id('Hello!')
# Prints 34936992

x = id(9999)
# Prints 33739544

L = ['red', 'green', 'blue']
x = id(L)
# Prints 33866256

class myfunc:
o = myfunc()
# Prints 33666912

Compare Two IDs

To check if two objects have same id, use is keyword.

# Check if 'x' and 'y' have the same id (point to the same object)
x = 42
y = x
print(x is y)
# Prints True

is keyword is used for identity (id) comparison, while == operator is used for equality (value) comparison.

Some Exceptions

In Python, every object has its own unique id. However, for the sake of optimization there are some exceptions.

Some objects have same id (actually one object with multiple pointer), like

  • Small integers between -5 and 256
  • Small interned strings (usually less than 20 character)
print(30 is 20+10)
# Prints True

print('aa'*2 is 'a'*4)
# Prints True


Python Example for Beginners

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There are two sides to machine learning:

  • Practical Machine Learning:This is about querying databases, cleaning data, writing scripts to transform data and gluing algorithm and libraries together and writing custom code to squeeze reliable answers from data to satisfy difficult and ill defined questions. It’s the mess of reality.
  • Theoretical Machine Learning: This is about math and abstraction and idealized scenarios and limits and beauty and informing what is possible. It is a whole lot neater and cleaner and removed from the mess of reality.

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