New assignmens ...

Avi Gross avigross at
Sun Oct 24 19:46:18 EDT 2021

No, many things need not be as general as possible once you consider how
much work it may take to develop code and how many bugs and oddities might
be introduced and even how much it may slow the interpreter.

I could make an argument that everywhere you can put in a character string
should also allow a regular expression but why? It makes no sense to allow
you to supply a filename to create using a regular expression as you are not
matching anything. Worse, perfectly valid string that may contain a dollar
sign or period or many other characters used in regular expression may
really be messed up if evaluated as a regular expression. So is it any
wonder NOBODY suggests the above be done? 

As Chris has said, something was added to Python that is a partial
implementation. There are fairly reasonable ways to do additional things and
until recently, those were the proper and only way. But the recent change
does not preclude a later upgrade if anyone is not only convinced it is
worth doing but of higher priority than the scarce resources needed to do
lots of other worthy and requested things including fixing bugs. 

I imagine you can create some fairly complex examples you can suggest should
be handled for generality including some very indirect references created
dynamically. The code to recognize any abstract use of symbols may not only
slow down every operation of even the simplest type but generate all kinds
of error messages nobody will understand, let alone translate into other
languages properly! Right now, it is simpler. An error message can say that
only certain simple usages are allowed. 

Now if anyone wants to donate a few hundred thousand dollars if used to make
the change, or offer to do it free, who knows? Of course, this means anyone
using the feature may need to check your version of Python to see if the
feature exists before ...

-----Original Message-----
From: Python-list < at> On
Behalf Of Alan Bawden
Sent: Sunday, October 24, 2021 3:53 AM
To: python-list at
Subject: Re: New assignmens ...

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

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...

Alan Bawden

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