List comprehension on a nested list - How to do it in Python

0 votes

I have this nested list:

l = [['40', '20', '10', '30'], ['20', '20', '20', '20', '20', '30', '20'], ['30', '20', '30', '50', '10', '30', '20', '20', '20'], ['100', '100'], ['100', '100', '100', '100', '100'], ['100', '100', '100', '100']]

Now, what I want to do is convert each element in a list to float. My solution is this:

newList = []
for x in l:
  for y in x:
    newList.append(float(y))

But can this be done using nested list comprehension, right?

Nov 21, 2018 in Python by Anirudh
• 2,080 points
870 views

1 answer to this question.

0 votes

Not sure what your desired output is, but if you're using list comprehension, the order follows the order of nested loops, which you have backwards. So I got the what I think you want with:

[float(y) for x in l for y in x]

The principle is: use the same order you'd use in writing it out as nested for loops.

answered Nov 21, 2018 by Nymeria
• 3,540 points

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