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Python - Immutability

📌 What You Will Learn
  • Define immutability and what makes an object immutable
  • Identify the five fundamental data types in Python
  • Observe how reassignment creates new objects using id()
  • Compare immutable types like bytes with mutable types like bytearray
  • Explain why Python 3 has no separate char and long data types

Introduction

Python provides several built-in data types to store different kinds of values.

Among them, five data types are called Fundamental Data Types.

These data types are used frequently in Python programs.

Fundamental Data Types

The five fundamental data types in Python are:

  1. int
  2. float
  3. complex
  4. bool
  5. str

These are the basic data types used to store values in Python.

Character Data Type

Python does not have a separate char data type.

A single character is also stored as a str object.

Example - Character Data Type

🐍Code Cell
1c = 'a'
2 
3print(type(c))
Output
No output captured.

Long Data Type

In Python 2, there was a separate long data type.

In Python 3, the long data type has been removed.

All integer values, including very large numbers, are stored using the int data type.

What is Immutability?

An object is called Immutable if its value cannot be changed after it is created.

If you assign a new value, Python creates a new object instead of modifying the existing object.

Immutable Fundamental Data Types

The following fundamental data types are immutable:

  • int
  • float
  • complex
  • bool
  • str

Once an object of these types is created, its value cannot be changed.

Example 1 - Integer Immutability

🐍Code Cell
1a = 10
2 
3print(id(a))
4 
5a = 20
6 
7print(id(a))
Output
140731502731216
140731502731536

Observation

The memory address changes because Python creates a new object.

The existing integer object is not modified.

Example 2 - String Immutability

🐍Code Cell
1s = "Durga"
2 
3print(id(s))
4 
5s = "Python"
6 
7print(id(s))
Output
140731503210432
140731503211008

Observation

A new string object is created.

The previous string object remains unchanged.

Example 3 - bytes Immutability

🐍Code Cell
1x = [10, 20, 30, 40]
2 
3b = bytes(x)
4 
5print(b[0])
6 
7b[0] = 100
Output
10

TypeError: 'bytes' object does not support item assignment

Observation

Once a bytes object is created, its values cannot be changed.

The bytes data type is immutable.

Mutable Example

bytearray is almost the same as bytes.

The difference is that bytearray is mutable.

Its elements can be modified after creation.

Example - bytearray

🐍Code Cell
1x = [10, 20, 30, 40]
2 
3b = bytearray(x)
4 
5b[0] = 100
6 
7print(b)
Output
bytearray(b'\x64\x14\x1e(')

Difference Between Immutable and Mutable

Immutable Mutable
Object cannot be changed after creation. Object can be changed after creation.
A new object is created when the value changes. The same object is modified.

Fundamental Data Types Summary

Data Type Immutable
int ✔ Yes
float ✔ Yes
complex ✔ Yes
bool ✔ Yes
str ✔ Yes

Important Notes

  • Python has five fundamental data types: int, float, complex, bool, and str.
  • Python does not have a separate char data type.
  • A single character is stored as a str.
  • Python 3 does not have the long data type.
  • All fundamental data types are immutable.

Key Points

  • Fundamental data types are the basic data types in Python.
  • Python stores characters using the str data type.
  • Python 3 uses only the int data type for all integer values.
  • Immutable objects cannot be modified after creation.
  • When an immutable object's value changes, Python creates a new object.
  • bytearray is mutable, whereas bytes is immutable.

Quick Summary

Topic Description
Fundamental Data Types int, float, complex, bool, str
Character Type No separate char data type
Long Type Removed in Python 3
Immutable Types int, float, complex, bool, str
Mutable Example bytearray
Immutable Example bytes
📝 Key Takeaways
  • An immutable object's value cannot be changed after creation
  • The five fundamental data types are int, float, complex, bool, and str
  • When an immutable value changes, Python creates a new object
  • id() shows the memory address of an object
  • bytearray is mutable, whereas bytes is immutable

🧠 Test Your Knowledge

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