Credit

Citing Help

Make sure to record any outside resources you use and any discussion you have about the pset in the comments at the top of your submission file! Along with maintaining a record of your sources, this practice is a way to take notes on what you learn and discuss.

Overview

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

$ python credit.py
Number: 378282246310005
AMEX

Specification

  • In credit.py in ~/pset6/credit/, 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 1.0, 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/2021/summer/sentimental/credit

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

style50 credit.py

This problem will be graded only along the axes of correctness and style.

How to Submit

  1. Download your credit.py file by control-clicking or right-clicking on the file in CS50 IDE’s file browser and choosing Download.
  2. Go to CS50’s Gradescope page.
  3. Click “Problem Set 3.0: Sentimental (Credit)”.
  4. Drag and drop your credit.py file to the area that says “Drag & Drop”. Be sure it has the correct filename!
  5. Click “Upload”.

You should see a message that says “Problem Set 3.0: Sentimental (Credit) submitted successfully!” You won’t see a score just yet, but if you see the message then we’ve received your submission!