[Python-ideas] Allowing def to assign to anything

[Bruce Leban]

Decorators easily support this:

dispatch_table = {}
def dispatch(arg):
    def inner(func):
        dispatch_table[arg] = func
        return func
    return inner

@dispatch('foo')
def dispatch_foo(bar):
    pass


--- Bruce
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On Sun, Oct 25, 2015 at 11:02 PM, Alexander Walters <tritium-list at sdamon.com
> wrote:

> In my code, I write a lot of dispatch dictionaries (for lack of a switch
> statement, but I will not hold my breath for that).  In trying to make
> writing these dictionaries less annoying, I tend to use many lambdas.  I
> can let you guess at what problems that has resulted in.  Of course, the
> preferred way to write such dictionaries is by using a regular function,
> and adding that function to a dictionary.  This isn't exactly a problem -
> it works, and works well, but it is annoying to write, and leaves artifacts
> of those functions in module scope.  I propose a little bit of sugar to
> make this a little less annoying.
>
> If `def` is allowed to assign to anything (anything that is legal at the
> left hand side of an = in that scope), annoying artifacts go away.  The
> syntax I propose should be backwards compatible.
>
> ```
> dispatch = {}
>
> def dispatch['foo'](bar):
>     return bar * bar
> ```
>
> Does this make anything possible that is impossible now?  No.  But it does
> make the intent of the module author clear - the function is only ever
> intended to live inside that dict, or list, or other structure.  This, to
> me, is less annoying to write, and is more readable.  This obviously could
> be used outside of creating dispatch dictionaries, but that is the use case
> I would benefit from.
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