Is it possible to set multiple list elements using slice notation without inserting new elements?

Question

I'm trying to set several elements in a list with slice notation. For example, I'd like to set the 2nd and 3rd elements of a to 100 and 200, respectively:

a[1:2] = [100, 200]

but that is setting the 2nd element to 100 and inserting 200 instead of replacing the 3rd element. Is this even possible in Python (using Python 2.7 if that matters)? I could easily iterate, but I wanted a more elegant Pythonic solution (even if it might be considered less readable).

>>> a=[0]*4
>>> a
[0, 0, 0, 0]
>>> a[1:2] = [100,200]
>>> a
[0, 100, 200, 0, 0]
>>>

score 8 · Accepted Answer · edited May 23 '17 at 12:29

8

You meant to do a[1:3], not a[1:2]. Note the rules on Python slice indexing: the slice [start:end] goes from start to end-1.

a=[0]*4
a[1:3] = [100,200]
a
# [0, 100, 200, 0]

edited May 23 '17 at 12:29

Community

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answered Sep 01 '14 at 23:09

David Robinson

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Precisely. user748113, you should accept this as the correct answer. – Dan Lenski Sep 01 '14 at 23:12
Thanks! Can't believe I missed that :) – Sep 02 '14 at 23:30

Is it possible to set multiple list elements using slice notation without inserting new elements?

1 Answers1