Deep¶

There are 3 different ways to copy objects in python:

True Copy: ID or old object and new object are the same, therefore changing one object also changes the other
Shallow Copy: ID of old object and new object is different, therefore the number of contents and immutable contents can be changed by one that will not effect the other, HOWEVER mutable content copied are still linked between the two objects (ie: a = [[1,2],3], copy_a = [[1,2],3] the list [1,2] inside is the same ID, therefore changing the list in “a” will also change the list in “copy_a”
Deep Copy: creates new IDs for each object within (very slow!). There is no link between old and new copy

For more description on mutable/immutable see builtin - Mutable/Immutable

For examples on copy see List - Copy