What is the difference between a deep copy and a shallow copy of a nested dictionary in Python?
Rashid D

In Python, when working with nested dictionaries, you have the option to make either a deep copy or a shallow copy. Understanding the difference between these two types of copies is crucial as it affects how changes to the original dictionary or the copied dictionary are reflected. 1. Shallow Copy: A shallow copy of a nested dictionary creates a new dictionary object but still references the same nested objects as the original dictionary. In other words, the outer dictionary is duplicated, but the inner objects are not. Both the original dictionary and the shallow copy contain references to the same inner objects. Consequently, changes made to the inner objects are reflected in both the original dictionary and the shallow copy. Here's an example of a shallow copy of a nested dictionary:

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import copy

original_dict = {"a": {"x": 1, "y": 2}, "b": {"z": 3}}
shallow_copy = copy.copy(original_dict)

shallow_copy["a"]["x"] = 100

print(original_dict)  # Output: {'a': {'x': 100, 'y': 2}, 'b': {'z': 3}}
print(shallow_copy)  # Output: {'a': {'x': 100, 'y': 2}, 'b': {'z': 3}}

In the above code,original_dict is the original nested dictionary, andshallow_copy is created using thecopy.copy() function. Modifying the inner object ({'x': 1, 'y': 2}) of theshallow_copy dictionary affects both theshallow_copy dictionary and theoriginal_dict. 2. Deep Copy: A deep copy of a nested dictionary creates a completely independent copy of both the outer dictionary and the inner objects. It creates a new dictionary object with duplicated inner objects. Consequently, changes made to the inner objects in one dictionary are not reflected in the other. Here's an example of a deep copy of a nested dictionary:

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import copy

original_dict = {"a": {"x": 1, "y": 2}, "b": {"z": 3}}
deep_copy = copy.deepcopy(original_dict)

deep_copy["a"]["x"] = 100

print(original_dict)  # Output: {'a': {'x': 1, 'y': 2}, 'b': {'z': 3}}
print(deep_copy)  # Output: {'a': {'x': 100, 'y': 2}, 'b': {'z': 3}}

In the above code, thedeepcopy() function from thecopy module is used to create a deep copy of theoriginal_dict. Modifying the inner object ({'x': 1, 'y': 2}) of thedeep_copy dictionary does not affect theoriginal_dict. To summarize, the key differences between a deep copy and a shallow copy of a nested dictionary in Python are: - Shallow copy creates a new dictionary object that references the same nested objects as the original dictionary, while deep copy creates a completely independent copy with duplicated inner objects. - Changes made to the inner objects in a shallow copy are reflected in the original dictionary, while changes in a deep copy do not affect the original dictionary. - Shallow copy is created using thecopy.copy() function, while deep copy is created using thecopy.deepcopy() function from thecopy module. Understanding these differences will help you choose the appropriate copy method for your nested dictionaries based on your requirements.

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