Why are we trying to write one-liners in the first place? Conditional expressions are a rare spice that should be used sparingly. No matter the syntax, three of them nested together isn't readable code, it's a puzzle.

Why are they a rare spice that should be used sparingly? Is it in line with python best practices? Anything to support this?

I think python list comprehensions is a direct antithesis to what you are saying. I thought they are considered to be a good and preferable practice, even nested cases.

We even got a new operator “:=“ to help us with those beautiful one-liners (or not) to move towards aesthetics and brevity.

Also, I disagree that the referred code isn’t readable. My point is exactly that such code is not readable and is a puzzle if current conditional expression is used. While having a more elegant if-else expression, this would not be a case.

Combination of list comprehensions, “:=“ operator and good conditional 1-liners could be an excellent toolkit to do complex things in simple, readable and brief manner. Now I think all is there, except if-else expression does not satisfy in either of those dimensions, namely brevity & readability (maybe it is better readable than C's for someone with major in languages…?).

So I am just trying to gauge if anyone else feels this way.

As I already said, my code would look fairly differently if anything similar to what I am proposing existed.

And I do not have a bias towards C or C++, 99% of what I do is python so if anything I am biased towards how python does things, not the other way round.

On 17 Jul 2023, at 23:09, Ned Batchelder <ned@nedbatchelder.com> wrote:
On 7/17/23 1:10 PM, Dom Grigonis wrote:
This whole thing started from dict’s `get` extension:
def get_substitute(self, key, default=None, subs=()):
    return key in self ? (self[key] := val in subs ? subs[val] : val) : default
I dare you to do a 1-liner with current if-else.
Why are we trying to write one-liners in the first place? Conditional expressions are a rare spice that should be used sparingly. No matter the syntax, three of them nested together isn't readable code, it's a puzzle.
--Ned.
On 17 Jul 2023, at 18:09, Rob Cliffe <rob.cliffe@btinternet.com> wrote:

On 15/07/2023 21:08, Dom Grigonis wrote:

Just to add. I haven’t thought about evaluation. Thus, to prevent evaluation of unnecessary code, introduction of C-style expression is needed anyways:

1. result = bar is None ? default : bar

The below would have to evaluate all arguments, thus not achieving benefits of PEP505.

2. result = ifelse(bar is None, default, bar)

So I would vote for something similar to:

result = bar is None ? default : bar

Where default and bar is only evaluated if needed. Although not to the extent as initially intended, it would offer satisfiable solutions to several proposals.

Well, default is only evaluated if needed; bar is always evaluated.
What is wrong with the Python equivalent

result = default if bar is None else bar
or if you prefer
result = bar if bar is not None else default

Perhaps you didn't know about this construction?

Best wishes
Rob Cliffe
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