Cc validator index question

Question

Its failing when im trying to modify the list by doubling every other index, aka the odd numver indices. Thanks for the help!

cardstring = input()
cardstring = list(cardstring)
revlist = cardstring.reverse()
[(x*2) if index(x) % 2 != 0 else x for x in revlist]
[(x-9) if x > 9 else x for x in revlist]
if len(revlist) == 16 and sum(revlist) % 10 == 0:
print("valid")
else:
print("not valid")

Answer 1

A few mentions. (to get you started)

reverse() is a method reverses an object in-place, it doesen't return anything
(hint use it correctly or use [::-1])

you need to assign to a variable your list comprehensions

in your list comprehensions you consider the members of the lists as int but they are strings.

list.index() is correct use of index()

Answer 2

Thanks!!! Will try and see what happens!

Answer 3

I didnt think i needed to return the reversed i thought i could just use it.
Can you give an example of how i should do the variable part?
So the list is all strings? How can i change the list to ints if its all numbers. Thanks!

Answer 4

Brenner Pieszak
revlist = cardlist[::-1]
or
cardstring.reverse() as third line

The var part:
revlist = [....your comprehension...]

From string to int
revlist = list(map(int, revlist))

Answer 5

cardstring = input()
cardstring = list(cardstring)
revliststring = cardstring.reverse()
revlist = list(map(int, revliststring))
revlist = [(x*2) if [x] % 2 != 0 else x for x in revlist]
revlist = [(x-9) if x > 9 else x for x in revlist]
if len(revlist) == 16 and sum(revlist) % 10 == 0:
print("valid")
else:
print("not valid")

Felt like i was on the right track but error at line 4, no clue where else to go from here.lol

Answer 6

Read here how to use reverse() method

https://www.w3schools.com/JUMP_LINK__&&__python__&&__JUMP_LINK/ref_list_reverse.asp

Edit. Though we already mention this in our previous answers