Python direct assignment, shallow copy, and deep copy parsing

• Direct Assignment: is actually the object's reference (alias).

• shallow copy (copy): copies the parent object and does not copy the inner sub-object of the object.

• deep Copy (deepcopy): The Deepcopy method of the Copy module, which completely copies the parent object and its child objects.

Example of a shallow copy of a dictionary

={1: [1,2,3]}

>>> b = a.copy() >>> a, b ({ 1 : [ 1 , 2 , 3 ]}, { 1 : [ 1 , 2 , 3 ]}) >>> a[ 1 ].append( 4 ) >>> a, b ({ 1 : [ 1 , 2 , 3 , 4 ]}, { 1 : [ 1 , 2 , 3 , 4 ]})

Deep copy requires the introduction of the Copy module:

Instance

1234567

>>>import copy>>> c = copy.deepcopy(a)>>> a, c({1: [1, 2, 3, 4]}, {1: [1, 2, 3, 4]})>>> a[1].append(5)>>> a, c({1: [1, 2, 3, 4, 5]}, {1: [1, 2, 3, 4]})

Analytical

1,B = A: assignment references, both A and B point to the same object.

2, B = a.copy (): shallow Copy, A and B are separate objects, but their child objects still point to a uniform object (which is a reference).

3, B = Copy.deepcopy (a): deep Copy, A and B completely copy the parent object and its child objects, both are completely independent.

Python direct assignment, shallow copy, and deep copy parsing