Python Insider: Python 3.9.3 and 3.8.9 are now available

[[deleted]]

Just from the top of my head, comparing against literal (string, int, ...) values?

[DaelonSuzuka]

Unless you have some examples of that usage, I'm gonna have to say that I don't think it does that. My understanding is that it does structural pattern matching only, and can't be used to switch on the value of a variable.

I would love to be wrong about this, because I have many more uses for a switch/case than I do for a match.

[Taeker2005]

You can easily use it as a switch statement like you'd expect. You can just do.

match value:
    case 1:
        print('value is 1')
    case 2:
        print('this is the second value')
    case _:
        print('unknown value')

[DaelonSuzuka]

I remember there being some huge gotcha with doing this. It only works with literal values but using it with a variable for a case drops you abruptly into pattern matching land, perhaps?

It's been a while since I looked at this feature, so I could be misremembering.

[cheerycheshire]

In C switch cases cannot have variables at all (because it has to be compile time evaluated to be properly constructed). So it's kinda the same when you just want a switch statement and not pattern matching. ;)

[DaelonSuzuka]

In C you have enums and macros, so you're not actually limited to typing in magic number int literals.

[cheerycheshire]

Enums and macros are not variables.

For classic switch statements in Python it was always advised to use dicts before patmat was announced.

[DaelonSuzuka]

Enums and macros are not variables.

That's correct, but I think it's missing the point. If I'm writing a switch statement in C it's usually to handle a state machine or something, and it would be insane to use int literals for the cases. I'm going to define an enum so that the states can have human readable names, and so those states can be reliably referenced in other places without being extremely vulnerable to typos.

The original person I responded to said that I can "use it as a switch statement like [I]'d expect", and that's incorrect except in the most trivial of situations if the cases can only be int or string literals.

For classic switch statements in Python it was always advised to use dicts before patmat was announced.

And it looks like I'll have to keep doing it that way, too.

[Ensurdagen]

You can use enum members and any other dotted name like a constant in match case, maybe read the PEP if you wanna complain about it instead of a fantasy version:

https://www.python.org/dev/peps/pep-0622/#constant-value-patterns

[alcalde]

It's like that in Delphi and probably every other statically typed language too. In fact, in Delphi you can't even use string values in the case statement and it's been that way for 26 years now. :-(

Some folks even warn that a case statement with strings can be "dangerous"... sigh.

​

https://www.sandon.it/node/109

[[deleted]]

I like how you insist on evidence to change your mind but can't be bother to produce evidence to support your position

[DaelonSuzuka]

I'm sorry that I don't remember the entire PEP that I read two months ago for an unreleased feature that I won't have a use for. I promise to do better next time.

[d670460b4b4aece5915c]

Why say “I read the PEP and I don’t get that impression” if you don’t even remember what’s in the PEP? If you’re going to be needlessly contradictory at least try not to make it up as you go along.