• Python Basics

  • Python Variables

  • Operators in Python

  • Conditional Statements in Python

  • Python Lists

  • Python Tuples

  • Python Sets

  • Python Dictionaries

  • Loops in Python

  • Python Arrays and Functions

  • Conclusion

Python Copy Dictionary

Copy Dictionaries in Python

In Python, dictionaries are mutable data structures that store data in key-value pairs. Sometimes, you may want to create a copy of a dictionary without linking it to the original. This lesson will guide you on how to copy dictionaries effectively in Python using different methods, ensuring that the copied dictionary is independent of the original.

1. Why Copy a Dictionary?

When you copy a dictionary, it is important to understand that a direct assignment (e.g., dict2 = dict1) does not create a new copy of the dictionary. Instead, it creates a reference to the original dictionary. Any changes made to one will affect the other.

Example: Direct Assignment Creates a Reference

python
1# Creating a dictionary
2original_dict = {
3    "brand": "Tesla",
4    "model": "Model 3",
5    "year": 2022
6}
7
8# Creating a reference to the original dictionary
9copied_dict = original_dict
10
11# Modifying the copied dictionary
12copied_dict["year"] = 2023
13
14print(original_dict)  # Output: {'brand': 'Tesla', 'model': 'Model 3', 'year': 2023}

In this example, changing copied_dict also changes original_dict because both variables point to the same dictionary.

2. Copying a Dictionary Using the copy() Method

One of the simplest ways to create a copy of a dictionary is by using the built-in copy() method. This method creates a shallow copy of the dictionary.

Example: Copying with the copy() Method

python
1# Creating a dictionary
2car_info = {
3    "brand": "Audi",
4    "model": "A4",
5    "year": 2021
6}
7
8# Making a copy of the dictionary
9car_copy = car_info.copy()
10
11print(car_copy)  # Output: {'brand': 'Audi', 'model': 'A4', 'year': 2021}

3. Copying a Dictionary Using the dict() Function

Another method to copy a dictionary is by using the built-in dict() function. This approach also creates a shallow copy.

Example: Copying with the dict() Function

python
1# Creating a dictionary
2laptop_info = {
3    "brand": "HP",
4    "model": "Pavilion",
5    "year": 2020
6}
7
8# Making a copy of the dictionary using dict()
9laptop_copy = dict(laptop_info)
10
11print(laptop_copy)  # Output: {'brand': 'HP', 'model': 'Pavilion', 'year': 2020}

4. Deep Copying a Dictionary

For nested dictionaries, where you want to copy all levels of the dictionary, you will need to create a deep copy using the copy module's deepcopy() method. This ensures that all levels of the original dictionary are copied, rather than just creating references.

Example: Deep Copying a Nested Dictionary

python
1import copy
2
3# Creating a nested dictionary
4nested_dict = {
5    "brand": "Apple",
6    "products": {
7        "phone": "iPhone",
8        "laptop": "MacBook"
9    }
10}
11
12# Making a deep copy of the nested dictionary
13nested_copy = copy.deepcopy(nested_dict)
14
15# Modifying the copy
16nested_copy["products"]["phone"] = "iPhone 14"
17
18print(nested_dict)  # Output: {'brand': 'Apple', 'products': {'phone': 'iPhone', 'laptop': 'MacBook'}}
19print(nested_copy)  # Output: {'brand': 'Apple', 'products': {'phone': 'iPhone 14', 'laptop': 'MacBook'}}

In this example, modifying nested_copy does not affect nested_dict, demonstrating the advantage of deep copying for nested structures.

Frequently Asked Questions