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Python | Ways to Copy Dictionary

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  • Last Updated : 30 Dec, 2022
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Dictionary is a collection which is unordered, changeable and indexed. In Python, dictionaries are written with curly brackets, and they have keys and values. It is widely used in day to day programming, web development, and machine learning. When we simply assign dict1 = dict2 it refers to the same dictionary. Let’s discuss a few ways to copy the dictionary from another dictionary. 
Method#1: Using copy() copy() method returns a shallow copy of the dictionary. It doesn’t take any parameter and return a new dictionary which is not referring to the initial dictionary. 

Python3




# Python3 code to demonstrate
# how to copy dictionary
# using copy() function
 
 
# initialising dictionary
test1 = {"name" : "akshat", "name1" : "manjeet", "name2" : "vashu"}
 
 
# method to copy dictionary using copy() function
test2 = test1.copy()
 
 
# updating test2
test2["name1"] ="nikhil"
 
# print initial dictionary
print("initial dictionary = ", test1)
 
# printing updated dictionary
print("updated dictionary = ", test2)

Output

initial dictionary =  {'name1': 'manjeet', 'name2': 'vashu', 'name': 'akshat'}
updated dictionary =  {'name1': 'nikhil', 'name': 'akshat', 'name2': 'vashu'}

Method #2: Using dict() The dict() is a constructor which creates dictionary in Python. 

Python3




# Python3 code to demonstrate
# how to copy dictionary
# using dict()
 
 
# initialising dictionary
test1 = {"name" : "akshat", "name1" : "manjeet", "name2" : "vashu"}
 
 
# method to copy dictionary using dict
test2 = dict(test1)
 
 
# updating test2
test2["name1"] ="nikhil"
 
# print initial dictionary
print("initial dictionary = ", test1)
 
# printing updated dictionary
print("updated dictionary = ", test2)

Output

initial dictionary =  {'name2': 'vashu', 'name': 'akshat', 'name1': 'manjeet'}
updated dictionary =  {'name2': 'vashu', 'name': 'akshat', 'name1': 'nikhil'}

Method#3 : Using Dictionary comprehension 

Python3




# Python3 code to demonstrate
# how to copy dictionary
# using dictionary comprehension
 
 
# initialising dictionary
test1 = {"name" : "akshat", "name1" : "manjeet", "name2" : "vashu"}
 
 
# method to copy dictionary using dictionary comprehension
test2 = {k:v for k, v in test1.items()}
 
 
# updating test2
test2["name1"] ="ayush"
 
# print initial dictionary
print("initial dictionary = ", test1)
 
# printing updated dictionary
print("updated dictionary = ", test2)

Output

initial dictionary =  {'name': 'akshat', 'name2': 'vashu', 'name1': 'manjeet'}
updated dictionary =  {'name': 'akshat', 'name2': 'vashu', 'name1': 'ayush'}

Method #4: Using copy module

One additional approach to copying a dictionary is to use the built-in function deepcopy from the copy module. This function creates a deep copy of the dictionary, meaning that it creates a new dictionary object with new memory addresses for both the keys and the values in the original dictionary. This is useful if you want to create a completely independent copy of the dictionary and any nested objects it contains, such as lists or other dictionaries.

Here’s an example of how to use deepcopy to copy a dictionary:

Python3




from copy import deepcopy
 
# initializing dictionary
test1 = {"name": "akshat", "name1": "manjeet", "name2": "vashu"}
 
# method to copy dictionary using deepcopy
test2 = deepcopy(test1)
 
# updating test2
test2["name1"] = "nikhil"
 
# print initial dictionary
print("initial dictionary = ", test1)
 
# printing updated dictionary
print("updated dictionary = ", test2)

Output

initial dictionary =  {'name': 'akshat', 'name1': 'manjeet', 'name2': 'vashu'}
updated dictionary =  {'name': 'akshat', 'name1': 'nikhil', 'name2': 'vashu'}

The time complexity of using deepcopy to copy a dictionary is O(n), where n is the number of keys and values in the dictionary. The space complexity is also O(n), as a new dictionary object with n keys and values is created in memory.


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