How to append to a list inside of a list in python

Question

I'm having trouble adding numbers to a list that is already in a list. For example, say I'm given:

L = [[1, 2, 3], [100, 101, 102]]

I'm trying to append to L[1] to get:

L = [[1, 2, 3, 4, 5, 6], [100, 101, 102]]

The way I was going about this was L[1].extend([4, 5, 6]) but was getting the result None.

Any help would be appreciated.

user2357112 · Accepted Answer · 2014-03-26 23:08:15Z

First, that's L[0] you want to append to, not L[1]. Indices start at 0.

Second, L[0].extend([4, 5, 6]) will work fine. It modifies the list and returns None. Demo:

>>> L = [[1, 2, 3], [100, 101, 102]] >>> L[0].extend([4, 5, 6]) >>> L [[1, 2, 3, 4, 5, 6], [100, 101, 102]]

Just don't try to do anything with extend's return value, and you should be fine.

oh whoops, that was a typo, I meant L[0]. And thank you! I didn't know that it changed it, I thought the result meant that it didn't successfully extend it.

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