On 2021-12-01 18:35, Chris Angelico wrote:
In my reference implementation, there is no object that stores it;
it's simply part of the function. A good parallel is the if/else
expression:
x = float("inf") if z == 0 else y/z
Is there an object that represents the if/else expression (or the
deferred "y/z" part)? No, although it could be implemented that way if
you chose:
This is not a good parallel. There is nothing deferred there. The
entire line is evaluated when it is encountered and you get a result and
no part of the if/else expression can ever impact anything else again
unless, via some external control flow, execution returns and
re-executes the entire line. That is not comparable to a function
default, which is STORED and evaluated later independently of the
context in which it was originally written (i.e., the function default
is re-executed but the function definition itself is not re-executed).
The ternary expression vanishes without a trace by the next line,
leaving only its evaluated result. There would be no use in being able
to access some part of it, since the whole (i.e., the ternary
expression) is completely finished by the time you would be able to
access it. This is not the case with a function definition. The
function definition leaves behind a function object, and that function
object needs to "know" about the late-bound default as an independent
entity so that it can be evaluated later. It is bad for the function to
store that late-bound default only in some private format for its
exclusive future use without providing any means for other code to
access it as a first-class value.
--
Brendan Barnwell
"Do not follow where the path may lead. Go, instead, where there is no
path, and leave a trail."
--author unknown
_______________________________________________
Python-ideas mailing list -- python-ideas@python.org
To unsubscribe send an email to python-ideas-le...@python.org
https://mail.python.org/mailman3/lists/python-ideas.python.org/
Message archived at
https://mail.python.org/archives/list/python-ideas@python.org/message/43TVQCJ62PJ2ZRCYFC7M467CYJOXA6FP/
Code of Conduct: http://python.org/psf/codeofconduct/
