strange behavior in copying array element to array in python

Question

I'm facing a strange issue related to copying array elements inside other arrays, let me explain with a code:

I'm loading a csv into a bidimensional array, if I do something like this:

e = [None] * 4
with open("file.csv") as f:
    for line in f:
        e=line.split(",")
        finalarray.append(e)

If I do this, in finalarray I got only the last csv entry repeated all the time, but, if I do this:

 with open("file.csv") as f:
        for line in f:
            finalarray.append(line.split(","))

works like a charm, but I cannot undestand why the second option works and the first one fails loading always the last csv entry.

Kind regards, and thanks in advance.

both should work, although it would be better to use the csv module. Are you sure that this is your code? [mcve] please — Jean-François Fabre, Jan 14 '18 at 21:27
There is no reason for both of these to behave differently. Probably you did something earlier which you failed to write here. — Moinuddin Quadri, Jan 14 '18 at 21:28
I suspect something like this: https://stackoverflow.com/questions/240178/list-of-lists-changes-reflected-across-sublists-unexpectedly — Jean-François Fabre, Jan 14 '18 at 21:28
Nitpick: "into a bidimensional array" no, you are using a list that contains other lists. — juanpa.arrivillaga, Jan 14 '18 at 21:29
Key issue here: where is `finalarray` defined? Please provide a [mcve] — juanpa.arrivillaga, Jan 14 '18 at 21:40

score -2 · Answer 1 · answered Jan 14 '18 at 21:34

-2

I think the problem is the e init.

We are using references to the same value, so, when you change the value, you change all the references. And the last value es the last entry in the CSV.

answered Jan 14 '18 at 21:34

Ferran

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... but you immediately discard `e` so it shouldn't matter. – juanpa.arrivillaga Jan 14 '18 at 21:36

strange behavior in copying array element to array in python

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