Using one line in Try in python

Question

I'm studying CS50p and the tutor says it's best practice to have as few lines as possible, ideally one, in a Try, but I really struggle to do this.

How could I write the following code so that I only try the input?

while True:
    try:
        # How to have just 1 line in try??
        order = input("Order: ").title().strip()
        if order in menu:
            price += menu[order]
            print(f"Total: ${price}")
    except (EOFError, KeyError):
        break

Answer 1

The reason why it's generally a best practice to have as few lines as possible in the body of a try statement is to make sure there is only one possible source that produces the exception being handled so that the logics of the exception handler can be tailored specifically to the nature of the error.

In your case, EOFError can only be raised by the input function, and KeyError can only be raised by a missing key from accessing menu[order], so you can enclose those two specific statements in try statements instead:

while True:
    try:
        order = input("Order: ").title().strip()
    except EOFError:
        break
    if order in menu:
        try:
            price += menu[order]
        except KeyError:
            break
        print(f"Total: ${price}")

But KeyError is unlikely to occur since you already put menu[order] in an if condition of order in menu, so you can remove the if condition to adopt an EAFP code pattern:

while True:
    try:
        order = input("Order: ").title().strip()
    except EOFError:
        break
    try:
        price += menu[order]
    except KeyError:
        break
    print(f"Total: ${price}")