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Python Introducing Lists Build an Application Display the List

What about using sys.exit instead of break?

In an earlier video, Craig used sys.exit expression to break out of a program. Is there a difference between that and the break code used here?

1 Answer

Chris Freeman
MOD
Chris Freeman
Treehouse Moderator 67,736 Points

Hey nicolaspeterson, good question! The semantic difference is break ends the innermost loop while sys.exit() exits the entire program.

In Craig’s code, the while can only be exited when “DONE” is entered. The break ends the while loop. After breaking, only the single statement show_list() is run before the program ends.

Given this is the only way the program ends, the break could be replaced with:

    if new_item == DONE:
        # break
        show_list()
        sys.exit()

A downside to this new approach is less readability. The exit is buried inside a loop. Given the purpose of the while loop is to process input. Adding “exit the program” to its responsibilities muddies the intent of the loop.

If this code block were to be used within another larger program, then it takes away exit control from the larger program which limits this codes ability to be reused. It is much better to let the code end “pythonically” by falling off the end of the module (or by calling a specifically written cleanup before exit function, if needed)

Post back if you need more help. Good luck!!!

Clear and concise as always, thank you!