python list of list unlinking the object

Question

I have two list that I combine into a single list. Later I want to make a copy of this list so I can do some manipulation of this second list without affecting my first list. My understanding is if you use this [:] it should unlink the list and make a second copy of the list in a independent memory location. My problem is Im not see that work for this scenario I have. I have also tried using list command as well, but the result was the same. a = ['a','b','c'] b = ['1','2','3'] c = [a[:],b[:]] # list of list d = c[:] # want to create copy of the list of list so I can remove last item for item in d: del item[-1] # this is what I am getting returned. In [286]: c Out[286]: [['a', 'b'], ['1', '2']] In [287]: d Out[287]: [['a', 'b'], ['1', '2']] JavaScript questions and answers, JavaScript questions pdf, JavaScript question bank, JavaScript questions and answers pdf, mcq on JavaScript pdf, JavaScript questions and solutions, JavaScript mcq Test , Interview JavaScript questions, JavaScript Questions for Interview, JavaScript MCQ (Multiple Choice Questions)

Answer 1

[:] only makes a shallow copy. That is, it copies the list itself but not the items in the list. You should use copy.deepcopy. import copy d = copy.deepcopy(c) Think of a list as having pointers to objects. Now your variable is a pointer to the list. What [:] does is create an entirely new list with the same exact pointers. copy.deepcopy copies all attributes/references within your object, and the attributes/references within those attributes/references.