To illustrate, enumerate () returns a generator for. Formally, enumerate gives you a generator that provides (index,element) pairs from a list. The check for whether i is odd is just (i % 2) = 1.īut what's a good way of getting to know both the index of the digit and the digit itself? Python has a nice built-in iterator called enumerate.
One possible answer is to somehow look up the index of the digit we are processing, and seeing if that one is odd or even. Instead of dividing the list up into evens and odds and separating the problems, what if we had some sort of indicator that we are processing an odd or an even digit? Correcting for the even numbers So what are the corrections we need to make? Well, every other digit needs to be added again. Return ( sum(temp_list) + CORRECTIONS ) % 10 = 0 Since both odds and evens adds each digit, we could start off with just adding up all the digits: def validate_credit_card_number(card_number): #incomplete code Then we also need to account for the cases when the doubling results in two-digit numbers, but more on that below. We will, in fact, also be adding up all the digits in evens, except we will also add them up again (doubling). Recall that for our sum, we will be adding up all the numbers in odds. Finding commonality in how the odds even digits are handled As a side-note about style, more descriptive names of these lists might be evens and odds: hints that would really help the person who has to read your code. If we desire to get a "one-liner" Python script, for what it's worth, let's look at the difference between list1 and list2. I should warn that the code is at a stage where optimizations begin to really flirt with readability, and so for shared code that must be understood and maintained, we're home safe.
#Credit card validator luhn algorithm how to
Josay's answer is right on the money in terms of how to start optimizing one's Python code.īelow I go further with the optimization that Josay started. Result=validate_credit_card_number(card_number) My code works, but I wanted to learn about a more efficient and more Pythonic way of doing this. I've implemented Luhn's algorithm for checking credit card numbers.
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