On Thu, May 27, 2021 at 04:53:17PM +0200, Ronald Oussoren via Python-ideas
wrote:
> Statics are still hidden global state
How are they *global* state when they are specific to an individual
function?
We can already get the basic behaviour of statics right now, only with
an ugly hack that pollutes the function parameter list and is
inconvenient to use.
static = [0]
def spam(arg, static=[0]):
static[0] += arg
return static[0]
def eggs(arg, static=[0]):
static[0] -= arg
return static[0]
Is it your argument that all three `static` variables are using shared
global state? If not, then I have no idea what you mean by insisting
that statics are "hidden global state". They are hidden state, but not
global. Just like closures and instance attributes.
> and those can be problematic regardless of being function local or
> module global. Having global state like this affects testability and
> can affect threading as well.
It sounds like your problem is with *mutable state* in general. Global
variables, instance attributes, class attributes, they all have exactly
the same issues.
So don't use mutable state. Nobody is forcing you to use this feature if
you prefer to write in a functional style with no mutable state.
> The factory function doesn’t need to be part of the public API of a
> module, I’ve used a pattern like this to create APIs with some hidden
> state:
>
> ```
> def make_api():
> state = ...
>
> def api1(…): …
> def ap2(…): …
>
> return api1, api2
> api1, api2 = make_api()
> ```
Congratulations, you've just used static local variables. You just used
closures for the implementation.
> I’m not saying that this is a particularly good way to structure code,
> in general just using a private module global is better (assuming the
> design calls for some kind of global state).
You: "Global state is bad! Don't use global state!"
Also you: "Don't use local state (closures)! Use global state, it's
better!"
*wink*
--
Steve
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