[Python-Dev] Subtle difference between f-strings and str.format()

[Serhiy Storchaka]

29.03.18 18:06, Terry Reedy пише:
> On 3/28/2018 11:27 AM, Serhiy Storchaka wrote:
>> The optimizer already changes semantic. Non-optimized "if a and True:" 
>> would call bool(a) twice, but optimized code calls it only once.
> 
> Perhaps Ref 3.3.1 object.__bool__ entry, after " should return False or 
> True.", should say something like "Should not have side-effects, as 
> redundant bool calls may be optimized away (bool(bool(ob)) should have 
> the same result as bool(ob))."

Do you meant that it should be idempotent operation? Because 
bool(bool(ob)) always have the same result as bool(ob)) if bool(ob) 
returns True or False.