python variable reassignment inside nested loops not working

Question

I am attempting to reassign variables inside nested for loops. I'd like to get the index for the number 6 inside a list of lists, but it's not working. Why isn't it working and how can I fix it?

Here's the code:

row = 0
col = 0
a = [[1, 2, 3, 4, 5], [3, 4, 4, 6, 9]]
for i in range(len(a)):
  for j in range(len(a)):
    if a[i][j] == 6:
      row = i # expect row = 1
      col = j # expect col = 3
print(row) # prints 0
print(col) # prints 0

TigerhawkT3 · Accepted Answer · 2019-02-24 04:45:08Z

4

row and col are not updated because the if statement is never executed. The loop with the j variable needs to be based on the length of a[i], not a, as a has a length of two while the lists inside it each have a length of 5. With that restriction, it's not finding the 6 element.

answered Feb 24, 2019 at 4:45

TigerhawkT3

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Tacratis · Accepted Answer · 2019-02-24 04:44:55Z

1

Your second line should iterate over the second dimension, so

  for j in range(len(a[i])):

answered Feb 24, 2019 at 4:44

Tacratis

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