Writing functions: Syntax summary

Here is a template for writing Python functions:

def function-name( parameter-list ):
    ...
    ... function-body
    ...
    return expression
    ...
    return expression

And here are a couple of guidelines:

• We prefer to have a single return expression as the last line of the function. If this guideline is followed then other programmers know where to look to find out what value is returned, and don't have to hunt through the function trying to spot all the return points. Having said that this is a preference not a requirement. Some code really is cleaner with multiple returns spread throughout the function, but this is unusual enough that you should do a quick mental check to verify that it is preferable.

• If you do not include a return statement, the value returned will the special value None, but it is better to be explicit that this is your intention by placing a blank return statement in the function than by just not having one (because then other programmers will not waste brain cycles wondering if you intended to return None, or forgot to include a return).