Python Basics Review Quiz

Great answer!

I just wanted to point out that out of the scope of this course, try actually has 4 parts; try, except, else and finally. The first three are exactly as you describe, but finally is the optional last part of the block that has some interesting properties. Whereas else will run in the event that there was no exception ( we can think of it like an if/else block - if exception, else) finally will run regardless of anything that happens in the try block - once you have entered the try block, finally will run no matter what.

On the face of it that can seem kind of redundant - couldn't we just put anything we wanted to run regardless of there being an error AFTER the try block? And most of the time you can, finally is more of a "you'll know it when you need it" kind of tool.

For example, even if you try to get out of a try block with continue, break or even the return statement, finally will still run, actually even if an error is raised that you didn't catch with an except block, it will still run. Here's an example of the return case:

def add_nums(a, b):
    try:
        a + b
    except TypeError:
        return "ops {} & {} aren't compatible types". format(
                                                            type(a).__name__, 
                                                            type(b).__name__
                                                            )
    else:
        return a + b

    finally:
        print("exited function")

print(add_nums(2, "2"))
print(add_nums(2, 2))

Will print:

exited function
ops int & str aren't compatible types
exited function
4

Because the finally clause happened before the result was returned to print. One quick gotcha - if you put a return in finally, it will override any return statements inside the try block that have already been run. So in this eacmple, if the finally block returned the string instead of printing it the output would look like this:

exited function
exited function

Thank you Jon Mirow for adding that extra info . I don't actually code in Python that often myself so I honestly forgot about the final part while writing my answer. But it is indeed a useful and important part of the try statement and you have done a great job explaining it.