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# Credit Card Validator / Python

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')

13th Jul 2023, 12:57 PM
BrightJ
3 ответов
+ 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)
13th Jul 2023, 7:14 PM
Slick
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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!
14th Jul 2023, 11:33 AM
BrightJ
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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
20th Jul 2023, 4:07 PM
Slick
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