# Learn How to Work with Numbers and Strings by Implementing the Luhn Algorithm - Step 19

### Tell us what’s happening:

I dont know if the for loop that I am using is placed and coded correctly.

the original code is this one:

def verify_card_number(card_number):
sum_of_odd_digits = 0
card_number_reversed = card_number[ :: -1]
odd_digits = card_number_reversed[ :: 2]
print(odd_digits)

``````
# User Editable Region

def verify_card_number(card_number):
sum_of_odd_digits = 0
card_number_reversed = card_number[::-1]
for digit in odd_digits:
odd_digits = card_number_reversed[::2]
print(digits)

# User Editable Region

def main():
card_number = '4111-1111-4555-1142'
card_translation = str.maketrans({'-': '', ' ': ''})
translated_card_number = card_number.translate(card_translation)

verify_card_number(translated_card_number)

main()
``````

User Agent is: `Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/123.0.0.0 Safari/537.36`
Your for loop is trying to access the `odd_digits` variable before it’s created.