Iterate two list with the same number of elements at once

Question

I am trying to figure out how to make those 2 for loops in just one. I tried to put together both for loops, but the output is a tuple, so it doesn`t work for me. And I am stucked in tryong to build a function:

for i in first:

if len(i) > 4:
print("Error: Numbers cannot be more than four digits.")
elif i.isalpha():
print("Error: Numbers must only contain digits.")
else:
if len(i) > maxlenf:
maxlenf = len(i)

for i in second:

maxlens=0

if len(i) > 4:
print("Error: Numbers cannot be more than four digits.")
elif i.isalpha():
print("Error: Numbers must only contain digits.")
else:
if len(i) > maxlens:
maxlens = len(i)

Somebody can help, please.

Answer 1

Please give sample data...because from what I can work out...your lists are lists of numbers as strings e.g:-
first = ["100", "200","300", "400"]
and not...
first = [100, 200, 300, 400] <== len and isalpha on each element will not work with this.

Answer 2

have you tried:
for i, j in zip(first, second) ?

Answer 3

The zip version mentioned by Angelo is nice.
Why do you think it is a problem? i is the element of first, j is the element of second list. In each iteration do the checks on i and j.

Maybe initialize the maxlen counters before the loop? Or is that on purpose?

Another way could be something like this:

for idx in range(0, len(first)):
# do sth with first[idx]
# do sth with second[idx]

Answer 4

yes, but the output is a tuple, so I don’t know how to process it afterwards...😩