Re:Python: copying a list the right way
by keeperofdakeys on Saturday November 05, 2011 @10:48PM
(#3201662)
Let's look at the line:
list1 = list2[:]
That line means "list1 is a list that has all the elements of list2", not "list1 is a new list that has all the elements of list2". It just happens that the implementation of slices in the python interpreter creates a new list for a slice. You may say it is 'obvious' that it works like that, in python, I will agree with you. You might not be able to say the same thing for other languages, especially if you haven't used them before.
The problem is, even with a simple knowledge of slices, someone reading your code may not realise that list1 is actually a new list; you are depending upon a side-effect of the language. If you used the Copy module, or even the list constructor, it would have been much clearer that list1 is a new list. This increases readability, which is very important if other people, or even yourself in the future re-read the code. Personally, I prefer readability in really long programs, and it isn't like you're programming C on an embedded device here.
The problem is, even with a simple knowledge of slices, someone reading your code may not realise that list1 is actually a new list; you are depending upon a side-effect of the language. If you used the Copy module, or even the list constructor, it would have been much clearer that list1 is a new list. This increases readability, which is very important if other people, or even yourself in the future re-read the code. Personally, I prefer readability in really long programs, and it isn't like you're programming C on an embedded device here.