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Credit - CS50x 2023

Implement a program that determines whether a provided credit card number is valid according to Luhn’s algorithm.

$ python credit.py
Number: 378282246310005
AMEX

Getting Started​

Log into cs50.dev, click on your terminal window, and execute cd by itself. You should find that your terminal window’s prompt resembles the below:

Next execute

wget https://cdn.cs50.net/2022/fall/psets/6/sentimental-credit.zip

in order to download a ZIP called sentimental-credit.zip into your codespace.

Then execute

unzip sentimental-credit.zip

to create a folder called sentimental-credit. You no longer need the ZIP file, so you can execute

rm sentimental-credit.zip

and respond with “y” followed by Enter at the prompt to remove the ZIP file you downloaded.

Now type

followed by Enter to move yourself into (i.e., open) that directory. Your prompt should now resemble the below.

Execute ls by itself, and you should see credit.py. If you run into any trouble, follow these same steps again and see if you can determine where you went wrong!

Specification​

  • In credit.py, write a program that prompts the user for a credit card number and then reports (via print) whether it is a valid American Express, MasterCard, or Visa card number, exactly as you did in Problem Set 1, except that your program this time should be written in Python.
  • So that we can automate some tests of your code, we ask that your program’s last line of output be AMEX\n or MASTERCARD\n or VISA\n or INVALID\n, nothing more, nothing less.
  • For simplicity, you may assume that the user’s input will be entirely numeric (i.e., devoid of hyphens, as might be printed on an actual card).
  • Best to use get_int or get_string from CS50’s library to get users’ input, depending on how you to decide to implement this one.

Usage​

Your program should behave per the example below.

$ python credit.py
Number: 378282246310005
AMEX

Hints​

  • It’s possible to use regular expressions to validate user input. You might use Python’s re module, for example, to check whether the user’s input is indeed a sequence of digits of the correct length.

Testing​

While check50 is available for this problem, you’re encouraged to first test your code on your own for each of the following.

  • Run your program as python credit.py, and wait for a prompt for input. Type in 378282246310005 and press enter. Your program should output AMEX.
  • Run your program as python credit.py, and wait for a prompt for input. Type in 371449635398431 and press enter. Your program should output AMEX.
  • Run your program as python credit.py, and wait for a prompt for input. Type in 5555555555554444 and press enter. Your program should output MASTERCARD.
  • Run your program as python credit.py, and wait for a prompt for input. Type in 5105105105105100 and press enter. Your program should output MASTERCARD.
  • Run your program as python credit.py, and wait for a prompt for input. Type in 4111111111111111 and press enter. Your program should output VISA.
  • Run your program as python credit.py, and wait for a prompt for input. Type in 4012888888881881 and press enter. Your program should output VISA.
  • Run your program as python credit.py, and wait for a prompt for input. Type in 1234567890 and press enter. Your program should output INVALID.

Execute the below to evaluate the correctness of your code using check50. But be sure to compile and test it yourself as well!

check50 cs50/problems/2023/x/sentimental/credit

Execute the below to evaluate the style of your code using style50.

How to Submit​

In your terminal, execute the below to submit your work.

submit50 cs50/problems/2023/x/sentimental/credit