Why Copy a Dictionary?

Copying a dictionary allows you to create a new dictionary with the same key-value pairs without affecting the original dictionary.

⚠️ Don't Copy Using Just = (Assignment)

original = {"name": "Alice", "age": 25}
copy_dict = original
copy_dict["age"] = 30
print(original)

Output:

{'name': 'Alice', 'age': 30}

Explanation: This doesn't copy the dictionary. It only creates a reference, so changes affect both variables.

Correct Ways to Copy a Dictionary

1. Using copy() Method

original = {"name": "Alice", "age": 25}
copy_dict = original.copy()
copy_dict["age"] = 30
print("Original:", original)
print("Copy:", copy_dict)

Output:

Original: {'name': 'Alice', 'age': 25}
Copy: {'name': 'Alice', 'age': 30}

Explanation: copy() creates a shallow copy — a new dictionary with the same contents.

2. Using dict() Constructor

original = {"name": "Bob", "age": 28}
copy_dict = dict(original)
copy_dict["age"] = 35
print("Original:", original)
print("Copy:", copy_dict)

Output:

Original: {'name': 'Bob', 'age': 28}
Copy: {'name': 'Bob', 'age': 35}

Explanation: dict() is another way to create a shallow copy of the dictionary.

3. Deep Copy for Nested Dictionaries

import copy
original = {
 "student": {
   "name": "Eve",
   "grade": "A"
 }
}
deep_copy_dict = copy.deepcopy(original)
deep_copy_dict["student"]["grade"] = "B"
print("Original:", original)
print("Deep Copy:", deep_copy_dict)

Output:

Original: {'student': {'name': 'Eve', 'grade': 'A'}}
Deep Copy: {'student': {'name': 'Eve', 'grade': 'B'}}

Explanation: copy.deepcopy() creates a full independent copy — even nested objects are cloned.

Summary of Dictionary Copy Methods

Conclusion

To safely copy a dictionary in Python, use .copy() or dict(). For nested structures, use copy.deepcopy() to avoid unexpected changes.