Credit Card Validator / Python

Question

Im done guys. I can solve every Medium Code Challenge except this one.
Pls dont give me new code, I want to understand the mistake in my code..

Problem:
https://www.sololearn.com/coach/96?ref=app

Code:
input = str(input())
input1= list(input)
#print(input)
i_rev = input1[::-1]
#print(i_rev )
new = []
for i in range(16):
if i % 2 == 0 or i == 0:
new.append(i_rev[i])
else:
new.append(str(int(i_rev[i])*2))
#print(new)
new1 = []
for i in new:
if int(i) > 9:
new1.append(str(int(i)-9))
else:
new1.append(i)
#print(new1)
sum = 0
for i in new1:
sum += int(i)
#print(sum)
if len(input) != 16:
print("not valid")
elif sum % 10 != 0:
print('not valid')
else:
print('valid')

Answer 1

1. never use base commands (ie 'input') as a variable name
2. the challenge says to multiply each 2nd digit by 2, your first for loop has a logic error in that when i == 1, it's actually the 2nd item in the list.
(i == 2 is the 3rd and i == 3 is the 4th because we start at 0)

Answer 2

Slick thx for the answer - I'm going to avoid mistake 1.
For mistake 2 - pls activate the 'print(i_rev)' and 'print(new)' line of my code. You will see that it works and that the second digit is multiplied by 2 - I used the else statement for the multiplication wirh 2.
So I cant see your point on that one. Pls explain it to me again, im a beginner.

Thx so much!

Answer 3

Hey, I checked it and it checks out. I can't see the hidden test cases so I can't tell without it and the code is a little complicated with all the new lists and variables. Check this code out and see if you can reimagine yours. It's a little more clear cut.

All "enumerate" does is takes a list and creates another list of tuples containing 2 values, the first is the index number and the second is the actual value. So:

a = ['a', 'b', 'c']
print(enumerate(a))

# output
[(0, 'a'), (1, 'b'), (2, 'c')]

https://code.sololearn.com/c8VH9QvtNn52/?ref=app