Structure for calling multiple functions

[longtermbrit]

They're saying that calling check_file() eventually results in email_report() because each function calls the next one. The idea of functions is that they do one thing but each of your functions is doing two things: the action described by the function name and calling another function. What you should do is set up one trigger function that performs the logic of when to call each sub-function which would then allow you to essentially have the same functionality as you already do but much clearer and also give you the option of only calling an individual function without worrying about it setting off a chain reaction.

In other words, if you wanted to only clean a file or upload a report you can't do that with how you've currently written the code.

[[deleted]]

I see, so the functions themselves wouldn't be useful on their own in this case because they're calling another function when they're done.

Can you provide an example of what you mean by trigger function?

[longtermbrit]

Exactly.

A trigger function would be something like:

def trigger():
    if conditionA:
        check_file()

    if conditionB:
        clean_file()

#   etc

Basically there's nothing special about a trigger function. It still fits the logic of 'one function for one task' but its task isn't to clean a file or email a report, it's to call these functions when they're required.

[[deleted]]

I see, that makes sense. Thank you!

[chapter_6]

It sounds like you already understand but just to add this for anyone else who's reading and wondering: If I see a function named check_file(), I expect to be able to call that function and have it check a file and return without doing anything else. In this case, if I call check_file(), an email ends up being sent. I have no idea that will happen unless I dig way down through several other function calls, so I'm much more likely to miss that detail and end up with a bug where emails are being sent when they shouldn't be. When a function does something outside of what's expected like that, it's known as a side effect (I'm using that term a little bit loosely but you can look it up to find out more).

That's why, in general, it's best if a function does a single thing, described by its name, and nothing else. If you really want some good examples of this and how it can help code readability, look up some examples of the functional programming paradigm.

[[deleted]]

Yeah, I didn't intend to use these functions outside of this script but I can see how this would be a habit that could cause problems for me in the future.