[Python-Dev] Issue #26204: compiler now emits a SyntaxWarning on constant statement

[Andrew Barnert]

On Tuesday, February 9, 2016 8:14 AM, Michel Desmoulin <desmoulinmichel at gmail.com> wrote:

> I give regular Python trainings and I see similar errors regularly such as:
> 
> - not returning something;
> - using something without putting the result back in a variable.
> 
> However, these are impossible to warn about.
> 
> What's more, I have yet to see somebody creating a constant and not 
> doing anything with it. I never worked with Ruby dev though.
> 

> My sample of dev is not big enough to be significant, but I haven't met 
> this issue yet. I still like the idea, anything making Python easier for 
> beginers is a good thing for me.

What idea do you like? Somehow warning about the things that are impossible to warn about? Or warning about something different that isn't any of the things your novices have faced? Or...?

> One particular argument against it is the use of linters, but you must 
> realize most beginers don't use linters.

That doesn't mean the compiler should do everything linters do.

Rank beginners are generally writing very simple programs, where the whole thing can be visualized at once, so many warnings aren't relevant. And they haven't learned many important language features, so many warnings are relevant, but they aren't prepared to deal with them (e.g., global variables everywhere because they haven't learned to declare functions yet). As a teacher, do you want to explain all those warnings to them? Or teach them the bad habit of ignoring warnings? Or just not teach them to use linters (or static type checkers, or other such tools) until they're ready to write code that should pass without warnings?

Part of learning to use linters effectively is learning to configure them. That's almost certainly not something you want to be teaching beginners when they're just starting out. But if the compiler started adding a bunch of warnings that people had to configure, a la gcc, you'd be forced to teach them right off the bat.

And meanwhile, once past the initial stage, many beginners _do_ use linters, they just don't realize it. If you use PyCharm or Eclipse/PyDev or almost any IDE except IDLE, it may be linting in the background and showing you the results as inline code hints, or in some other user-friendly way, or at least catching some of the simpler things a linter would check for. Whether you want to use those tools in your teaching is up to you, but they exist. And if they need any support from the compiler to do their job better, presumably they'd ask for it.

> They are part of a toolkit you learn to use 

> on the way, but not something you start with. Besides, many people using 
> Python are not dev, and will just never take the time to use linters, 
> not learn about them.


If people who aren't going to go deep enough into Python to write scripts longer than a page don't need linters, then they certainly don't need a bunch of warnings from the compiler either.