How do I copy a list in an iteration?

Question

I need to make a copy of a list from a list of lists. The following code gives an error message:

y = list[x]
TypeError: unsubscriptable object

a = [[0],[1]]
for x in a:
    y = list[x]
    print y

What am I doing wrong here?

There are some intersting (and fast) answers here: http://stackoverflow.com/questions/952914/making-a-flat-list-out-of-list-of-lists-in-python — Ofir Baruch, Mar 09 '12 at 20:47
possible duplicate of [Flattening a shallow list in Python](http://stackoverflow.com/questions/406121/flattening-a-shallow-list-in-python) — wberry, Mar 09 '12 at 20:49

veiset · Accepted Answer · 2012-03-09T21:00:46.473

4

y = list[x]

Are you sure you aren't meaning to call the list constructor with the variable x as a parameter, instead of trying to access the element 'x' in the variable 'list'? As in:

y = list(x)

edited Mar 09 '12 at 21:00

answered Mar 09 '12 at 20:43

veiset

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Note that this isn't "casting" per se, but rather "calling the list constructor". – Ignacio Vazquez-Abrams Mar 09 '12 at 20:46
@veiset: You know that you can edit the answer and make it a bit more precise? – Niklas B. Mar 09 '12 at 20:52

score 0 · Answer 2 · answered Mar 09 '12 at 20:46

0

y=list(x)

The above one should work fine

answered Mar 09 '12 at 20:46

Teja

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score 0 · Answer 3 · answered Mar 09 '12 at 20:47

list is actually the type, so it makes no sense to try and get its x element. If you want to instantiate a list, you need to use list(iterable).

Now, if you want to copy a list, the simpler solution would be to use the copy module.

import copy
a = [[0],[1]]
new_list = copy.copy(a[0])

Pay attention to the fact that if you want to copy an item with nested elements, you'll have to use copy.deepcopy.

How do I copy a list in an iteration?

3 Answers3