How to copy a dictionary and only edit the copy

Question

Can someone please explain this to me? This doesn\'t make any sense to me.

I copy a dictionary into another and edit the second and both are changed. Why is this hap

Answer 1

The best and the easiest ways to create a copy of a dict in both Python 2.7 and 3 are...

To create a copy of simple(single-level) dictionary:

1. Using dict() method, instead of generating a reference that points to the existing dict.

my_dict1 = dict()
my_dict1["message"] = "Hello Python"
print(my_dict1)  # {'message':'Hello Python'}

my_dict2 = dict(my_dict1)
print(my_dict2)  # {'message':'Hello Python'}

# Made changes in my_dict1 
my_dict1["name"] = "Emrit"
print(my_dict1)  # {'message':'Hello Python', 'name' : 'Emrit'}
print(my_dict2)  # {'message':'Hello Python'}

2. Using the built-in update() method of python dictionary.

my_dict2 = dict()
my_dict2.update(my_dict1)
print(my_dict2)  # {'message':'Hello Python'}

# Made changes in my_dict1 
my_dict1["name"] = "Emrit"
print(my_dict1)  # {'message':'Hello Python', 'name' : 'Emrit'}
print(my_dict2)  # {'message':'Hello Python'}

To create a copy of nested or complex dictionary:

Use the built-in copy module, which provides a generic shallow and deep copy operations. This module is present in both Python 2.7 and 3.*

import copy

my_dict2 = copy.deepcopy(my_dict1)