Python

copy() method in dictionary

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copy() method in dictionary - Python

This method is used to create a shallow copy of a dictionary.

The .copy() method doesn’t take any argument.

It returns a copy of a dictionary.

When we call this method with a dictionary it will create a new dictionary in the backend and iterate over the items of the original dictionary and every item will be appended to the new dictionary, finally it will return a newly copied dictionary.

It returns a shallow copy of a dictonary which means when we modify the original dictionary it will not affect the copied dictionary and vice versa.

The time complexity of this method is O(n) where n is the number of items in original dictionary

Syntax –

dictionary.clear()

Parameters –

argument → Doesn’t take any argument

return → return a shallow copy of a dictionary

Example 1 –

				
					my_dict={'one':1,'two':2,'three':3,'four':4,'five':5}
print("Original dictionary:\n",my_dict)

copied_dictionary=my_dict.copy()
print("Copied dictionary:\n",copied_dictionary)

# Output -
# Original dictionary:
# {'one': 1, 'two': 2, 'three': 3, 'four': 4, 'five': 5}
# Copied dictionary:
# {'one': 1, 'two': 2, 'three': 3, 'four': 4, 'five': 5}

In the above example, first we create a dictionary with some items and store it in my_dict variable.

After creating my_dict print the original dictionary on the output screen.

Then create a copy of the original dictionary using the .copy() method and store the copied dictionary in the copied_dictionary variable.

Finally, print the copied dictionary on the output screen.

Example 2- Let’s see if modifying the original dictionary affects the copied dictonary or not.

				
					dct={'vowels':['a','e','i','o','u'],'hello':'world!'}
print("Original Dictionary:\n",dct)

dct_copy=dct.copy()
print("Copied dictionary:\n",dct_copy)
dct['hello']='Python'
print("Modify original dictionary:\n",dct)
print("Copied dictionary:\n",dct_copy)

# Output -
# Original Dictionary:
# {'vowels': ['a', 'e', 'i', 'o', 'u'], 'hello': 'world!'}
# Copied dictionary: 
# {'vowels': ['a', 'e', 'i', 'o', 'u'], 'hello': 'world!'}
# Modify original dictionary: 
# {'vowels': ['a', 'e', 'i', 'o', 'u'], 'hello': 'Python'}
# Copied dictionary: 
# {'vowels': ['a', 'e', 'i', 'o', 'u'], 'hello': 'world!'}

Example 3- create a copy of a dictionary without using an in-built method e.g. .copy()

				
					student = {
    "name": "ABC",
    "age": 20,
    "major": "Computer Science",
    "grades": [90, 85]
}
new_dict={}
for key, value in student.items():
    new_dict[key] = value
print("Original dictionary:\n",student)
print("Copied dictionary:\n",new_dict)

# Output -
# Original dictionary:
# {'name': 'ABC', 'age': 20, 'major': 'Computer Science', 'grades': [90, 85]}
# Copied dictionary:
# {'name': 'ABC', 'age': 20, 'major': 'Computer Science', 'grades': [90, 85]}

Example –

				
					my_dict={'A':10,'B':20,'C':30,'D':40,'E':50}
my_dict1=my_dict1
print("Original dictionary:\n",my_dict)
print("Copied dictionary:\n"my_dict1)
my_dict.update({'F':60})
print("\nModified original dictionary:\n",my_dict)
print("Copied dictionary:\n",my_dict1)

# Output -
# Original dictionary:
# {'A': 10, 'B': 20, 'C': 30, 'D': 40, 'E': 50}
# Copied dictionary: 
# {'A': 10, 'B': 20, 'C': 30, 'D': 40, 'E': 50}

# Modified original dictionary: 
# {'A': 10, 'B': 20, 'C': 30, 'D': 40, 'E': 50, 'F': 60}
# Copied dictionary: 
# {'A': 10, 'B': 20, 'C': 30, 'D': 40, 'E': 50, 'F': 60}

In the above example, you can see that when we modify the original dictionary it modifies the copied dictionary as well.

This is because we do not create a copy of the original dictionary instead of creating a copy we create another reference of the original dictionary object that’s why it happens.

In this situation, if we modify any dictionary the changes will affect both the dictionary.

Python

copy() method in dictionary

copy() method in dictionary - Python

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