[Python-ideas] (try-except) conditional expression similar to (if-else) conditional (PEP 308)

[MRAB]

Jan Kaliszewski wrote:
>> Syntax Ideas:
>>     Option 1:
>>         x = float(string) except float('nan') if ValueError
>>         op(float(string) except float('nan') if ValueError)
> 
> -0.5
> I wouldn't mix up 'if' word with 'except' -- there are different concepts.
> 
>>     Option 2:
>>         x = float(string) except ValueError: float('nan')
>>         op(float(string) except ValueError: float('nan'))
> 
> +0.5
> IMHO seems to be the best of the propositions. I'd add to it optional
> as (like in present 'try:... except Exc as exc:...')
> 
Can there be multiple 'except's?

     reciprocal = 1.0 / float(string) except ValueError: float('nan') 
except ZeroDivisionError: float('inf')

(We can already chain '==', etc.)

>>     Option 3:
>>         x = float(string) except ValueError else float('nan')
>>         op(float(string) except ValueError else float('nan'))
> 
> -1
> IMHO it's illogical. 'else' has completely opposite role in present
> 'try...except...' clauses. It'd be terribly missleading, not only
> for newbies.
>