Possible Luhn error

Exercism
1

My solution for Luhn passes all test but 4, 10 and 11. I have passed it through and IDE and return True for these tests but exercism says they return False. Can anyone see where I am going wrong if at all before I give up and move on to the next?

class Luhn:
def init(self, card_num):
self.card_num = (card_num)
self.number_valid = self.valid()

def valid(self):
    self.number_valid = True
    self.card_num = self.card_num.replace(" ", "")
    
    if len(self.card_num) < 2 or self.card_num.isdigit() == False:
        self.number_valid = False
        return self.number_valid
    self.card_num = (self.card_num)[::-1]

    doubled = 0
    for i, num in enumerate(self.card_num):
        n = int(num)
        if i % 2 == 1:
            n *= 2
            if n > 9:
                n -= 9
        doubled += n

    if doubled % 10 == 0:
        return self.number_valid
    self.number_valid = False
    return self.number_valid
2

Don’t make us go look it up: what are the inputs for those failing tests?

3

Sorry! Tests are:

“59”

“095 245 88”

“234 567 891 234”

4

Your code returns False because of the above code block.

5

Is it possible to give more details?

I have tried commenting out various parts of that code block without any change to the 3 test results.

I have ran is through the IDE here Python Tutor code visualizer: Visualize code in Python, JavaScript, C, C++, and Java

and the 3 tests return True so I am lost!

6

What is "095 245 88".is digit()?

7

Maybe I am missing something. I am new to this after all. But my understanding is that
“095 245 88”.is digit() would return False due to the spaces but that shouldn’t be a problem due the line in the block above being

self.card_num = self.card_num.replace(" ", “”)

Which should, and has on everywhere ive checked except exercism, return True.

Also that would not account for “59” failing.

Its possible, and probable im missing something obvious…

8

In your valid function, you do this

self.card_num = (self.card_num)[::-1]

where you overwrite the instance variable with its reverse value.

The tests create an instance and then call valid()

However in your constructor you do this

self.number_valid = self.valid()

You end up reversing the card number twice.

Remove that line from __init__

9

Great thank you. That fixed it.
The test creating an instance explains why ir worked when I transposed it into another IDE