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home / developersection / interviews / what is the difference between mutable and immutable types in python?
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Ravi Vishwakarma
Ravi Vishwakarma

IT-Hardware & Networking

Ravi Vishwakarma is a dedicated Software Developer with a passion for crafting efficient and innovative solutions. With a keen eye for detail and years of experience, he excels in developing robust software systems that meet client needs. His expertise spans across multiple programming languages and technologies, making him a valuable asset in any software development project.

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1 Answers

Ravi Vishwakarma
Ravi Vishwakarma 27 Mar 2025
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Mutable vs Immutable Types in Python

In Python, mutability refers to whether an object can be changed after it is created. Based on this, Python data types are classified as:

  1. Mutable → Can be modified after creation.
  2. Immutable → Cannot be modified after creation.

Mutable Types (Can Change)

These objects allow modifications without changing their identity (memory location).

Examples of Mutable Types

  1. list
  2. dict (dictionary)
  3. set
  4. bytearray

Example of a Mutable List

numbers = [1, 2, 3]
print(id(numbers))  # Memory address before modification

numbers.append(4)   # Modify list
print(numbers)      # [1, 2, 3, 4]
print(id(numbers))  # Memory address remains the same

Immutable Types (Cannot Change)

Once an object is created, it cannot be modified. Any modification creates a new object in memory.

Examples of Immutable Types

  1. int
  2. float
  3. bool
  4. tuple
  5. str
  6. frozenset
  7. bytes

Example of an Immutable String

name = "Hello"
print(id(name))  # Memory address before modification

name += " World"  # Attempting to modify
print(name)      # "Hello World"
print(id(name))  # Memory address changes (new object created)

Key Differences Between Mutable and Immutable Types

Feature Mutable Types (Changeable) Immutable Types (Unchangeable)
Modification Can be modified in place Cannot be modified once created
Memory Usage Same object remains in memory New object is created on change
Examples list, dict, set int, float, str, tuple
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