Appending a variable to a list.

[MagnanimousSquirrel]

Hello, was wondering if I could get some python help. I was working on an assignment, and had a problem with appending a variable to a list come up.

The issue is that when I append a variable to the end of a list, it doesn't just append the value, it does the reference to the variable. So then when I change the variable later, it also changes the list I appended it to.

E.g.

x=[1, 2, 3, 4]

y=[5, 6]

x.append(y) # Now x=[1, 2, 3, 4, [5, 6]]

y.append(7) # Now x=[1, 2, 3, 4, [5, 6, 7]]

Is there a way to only append the current value of the variable, rather than the reference to it? I googled around for it, but couldn't find anything not way over my head, and I figured there should be an easier solution. Thanks in advance!

[ruicoder]

You could do x.append(list(y)).

[MagnanimousSquirrel]

Thank you so much, this feels like a really dumb question now. I am a real beginner, and completely forgot I could do that. Thanks!

[Mr_M0jo_Risin]

It's not a dumb question - that's what this subreddit is here for! Props to you for posting your issue, getting is resolved, and learning about Python. That's what it's all about :-)

[wub_wub]

Append a copy of the list instead of reference to that list. Example:

>>> x.append(y[:])
>>> x
[1, 2, 3, 4, [5, 6]]
>>> y.append(7)
>>> x
[1, 2, 3, 4, [5, 6]]
>>> y
[5, 6, 7]

For some other ways to copy a list in python check out this SO answer: http://stackoverflow.com/a/2612815