New assignmens ...

Chris Angelico rosuav at
Sun Oct 24 11:18:27 EDT 2021

On Mon, Oct 25, 2021 at 2:13 AM Alan Bawden <alan at> wrote:
> It seemed weird to me that only an identifier was allowed to be the
> target of an assignment expression.  Then it occurred to me that
> function definitions are another place where only identifiers are
> allowed, but where I could imagine an attributeref or a subscription
> being used.  E.g.
>   def table[i](x):
>       ...
> would mean the same thing as:
>   def _temp_(x):
>       ...
>   table[i] = _temp_
> I don't immediately see that this would screw up the grammar in any way,
> so why not allow it?  A `def` statement is just another form of
> assignment, so just as for `:=` expressions, we should allow the target
> to be as general as possible!
> I'm guessing that about 70% of you will think that this is a horrible
> idea, 10% of you will find it compelling, and the remaining 20% will
> find themselves conflicted.  You can count me in that last category...

This has come up periodically, but it's a bit tricky to define some of
the edge cases, like what the function's name should be. But it would
definitely help with building dispatch tables. Currently, I tend to
build them with a decorator:

tools = {}
def tool(f):
    tools[f.__name__] = f
    return f

def frobnicate(): ...

def spamify(): ...

In theory, it would be possible to do this:

def tools["frobnicate"](): ...

But I'm not sure that it's truly better.


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