[Python-Dev] What's the status of PEP 505: None-aware operators?

Serhiy Storchaka storchaka at gmail.com
Wed Nov 29 03:06:32 EST 2017

28.11.17 22:31, Raymond Hettinger пише:
>> I also cc python-dev to see if anybody here is strongly in favor or against this inclusion.
> Put me down for a strong -1.   The proposal would occasionally save a few keystokes but comes at the expense of giving Python a more Perlish look and a more arcane feel.
> One of the things I like about Python is that I can walk non-programmers through the code and explain what it does.  The examples in PEP 505 look like a step in the wrong direction.  They don't "look like Python" and make me feel like I have to decrypt the code to figure-out what it does.
>      timeout ?? local_timeout ?? global_timeout
>      'foo' in (None ?? ['foo', 'bar'])
>      requested_quantity ?? default_quantity * price
>      name?.strip()[4:].upper()
>      user?.first_name.upper()

New syntax often look unusual. "lambda" and "yield" also didn't "look 
like Python".

But there are other considerations.

1. Languages that has the ?? and ?. operators usually have a single 
special (or at least a one obvious) value that is served for signaling 
"there-is-no-a-value". The None in Python is not so special. It can be 
used as a common object, and other ways can be used for denoting an 
"absent" value. The need of None-specific operators in Python is lower.

2. Python already have other ways for handling "absent" values: the 
short-circuit "or" and "and" operators which return the one of 
arguments, getattr() with the default value, the hack with default class 
attributes, exception handling. The need of the proposed operators in 
Python is lower.

3. These languages usually have borrowed the syntax of the ternary 
operator from C: "... ? ... : ...". Thus the syntax with "?" looks more 
natural in them. But in Python it looks less natural.

I'm -1 for accepting this syntax in 3.7. In future all can be changed.

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