Python Dict Copy vs Deepcopy

Aug 1, 2019

python

Copy

Shallow copy

data = {    'name': 'Desmond',    'friends': ['Jack', 'Mei Ru', 'Bob']}data2 = data.copy()data2['name'] = 'New Desmond'data2['friends'][0] = 'New Jack'print(data)

Output

{'name': 'Desmond', 'friends': ['New Jack', 'Mei Ru', 'Bob']}

NOTE: data['name'] does not change as the value is copied, but data['friends'] is an object/list where the value is not copied.

Deep Copy

import copydata = {    'name': 'Desmond',    'friends': ['Jack', 'Mei Ru', 'Bob']}data2 = copy.deepcopy(data)data2['name'] = 'New Desmond'data2['friends'][0] = 'New Jack'print(data)

Output

{'name': 'Desmond', 'friends': ['Jack', 'Mei Ru', 'Bob']}

NOTE: Both data['name'] and data['friends'] as deepcopy make a copy of basic value and object/list.

NOTE: copy and deepcopy are not thread-safe, use lock.

References:

https://docs.python.org/3/library/copy.html

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