How to change an elements in array of array?

Question

this is the code I have:

l = [[1,'a'],[2,'b'],[3,'c']]
n = []
for i in range(len(l)):
  n.append(l[i])
print(n)

I'm trying to select each element in the array to revers the number order only and putting it into a new array.

so I'm trying to get it to look like this:

[[3,'a'],[2,'b'],[1,'c']]

@blhsing's answer is fine as far as it goes. But since your question lacks enough context to know why you need that transformation it is impossible to know if that is a good answer. Especially in light of your solution which does nothing more than copy the l list to n with no transformation whatsoever. — Kurtis Rader
– Kurtis Rader, Commented Nov 6, 2018 at 3:11

blhsing · Accepted Answer · 2018-11-05 22:34:23Z

2

You can pair the reversed list with the list itself using zip in a list comprehension like this:

[[a, b] for (a, _), (_, b) in zip(reversed(l), l)]

This returns:

[[3, 'a'], [2, 'b'], [1, 'c']]

Or you can modify the list in-place by swapping items:

for i in range(len(l) // 2):
    l[i][0], l[len(l) - i - 1][0] = l[len(l) - i - 1][0], l[i][0]

l would become:

[[3, 'a'], [2, 'b'], [1, 'c']]

answered Nov 5, 2018 at 22:34

blhsing

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