Iterate through list using for-loop while adding numbers

Question

def tomtoCm(add):
    assert add > 0
    return add * 2.54



numbers = [4, 1, 20]

def numbersToCm(numbers):
     
    for i in numbers:
        convert = tomtoCm(numbers[0,1,2])
        print(convert)

numbersToCm(numbers)

I am struggling to * 2.54 to all my numbers in my list. I have tried using len and range, but I can't seem to do it quite right. If I for example write [0] the program prints out 10.16 three times. It won't iterate through my whole list

You never modify the list. And what is the purpose of tomtoCm(numbers[0,1,2])? — Guy
– Guy, Commented Oct 4, 2021 at 11:14
The code seem to be a bit of a mess, first of all, you are looping through the numbers list, but repeating the same items. Hence, you need to iterate through i instead of [0,1,2]. Also, I don't see why you need a seperate function for (tomtoCm) and (numbersToCm) when both can be made into one, making the code much simpler — Zaid Al Shattle
– Zaid Al Shattle, Commented Oct 4, 2021 at 11:19

Mureinik · Accepted Answer · 2021-10-04 11:19:45Z

2

With a for-in loop, you iterate over the list's elements, not its indexes. I.e.:

for i in numbers:
    convert = tomtoCm(i)
    print(convert)

Having said that, the more idiomatic approach would probably be to use a list comprehension:

updated_list = [tomtoCm(i) for i in numbers]
print(updated_list)

answered Oct 4, 2021 at 11:19

Mureinik

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3 Comments

Zaid Al Shattle Over a year ago

To add to this, you can also easily modify this list comprehension to skip the first function entirely as well (something like updated_list = [ i * 2.54 for i in numbers])

Mureinik Over a year ago

@ZaidAlShattle True 'dat. I wanted to keep OP's original function that has the added assertion, but it would probably be "cleaner" python to unwrap it

Zaid Al Shattle Over a year ago

Makes sense! Just wanted to add that note in case OP saw it. Cheers buddy

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