List comprehension on a nested list?

Question

I have this nested list:

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


        

Answer 1

Since i am little late here but i wanted to share how actually list comprehension works especially nested list comprehension :

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

is actually same as :

New_list=[]
for x in l:
    New_list.append(x)

And now nested list comprehension :

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

is same as ;

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

    new_list.append(sub_list)

print(new_list)

output:

[[40.0, 20.0, 10.0, 30.0], [20.0, 20.0, 20.0, 20.0, 20.0, 30.0, 20.0], [30.0, 20.0, 30.0, 50.0, 10.0, 30.0, 20.0, 20.0, 20.0], [100.0, 100.0], [100.0, 100.0, 100.0, 100.0, 100.0], [100.0, 100.0, 100.0, 100.0]]