PEP308: Yet another syntax proposal

Andrew Dalke adalke at
Tue Feb 11 21:08:21 CET 2003

Paul Rubin:
> I thus have to ask: if CE's are so rare, then why does the subject
> matter to you?  You won't be required to use them in your own code if
> they're added.  And according to your own statistics, you'll very
> seldom have to deal with them in other people's code either.
> So I'm sorry, but it really sounds like you're trying to impose your
> stylistic preferences on other people without any practical
> justification.  The other CE opponents' posts don't give that
> impression nearly as much.

I generated two sets of statistics:
  1) use of if/else statements vs. if/else expression vs. short-circuiting
        if/else expression
  2) likelihood of misuse of the if/else expression, given more appropriate
         Python idioms

The later numbers suggest that whe I do "deal with them in other people's
code" then there is somewhere between a 25 to 50% that it will be be
used in place of more appropriate Python code.  This is based on
observing the misuse of ?: in existing C++ code, as in the following
(translated into Python)

n = obj.count() if obj is not None else 0
  .... skip a few lines

(Were this written as an if/else statement, the needless code would more
likely have been cleaned up, I think, because the decision point stands
out more.)

I also observed places where the ?: idiom in C does not naturally
fit a if/else expression in Python, because Python is a different language
than C, as in the following (assume the precondition that 0 <= i <= 15)

  if i < 10:
    hex_c = chr(48 + i)
    hex_c = chr(55 + i)

which in an PEP 308 world will likely be written as

  hex_c = chr(48 + i if i < 10 else 55 + i)

I find this to be less readable than the first case, and even less
readable than the more Pythonic (IMHO)

  hex_c = "0123456789ABCDEF"[i]

And I and others pointed out places where an if/else expression could
be used, but shouldn't because the code was less readable.  In that
case, I assigned a somewhat low probability (I think 25%) that the
less readable option would be taken.

Were there low chance of misuse, I would not be too concerned.
However, it is this high likelihood of misuse which causes me to be
against this syntax, and to keep posting these statistics.

                    dalke at

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