is @ operator popular now?

[Peter Otten]

Chris Angelico wrote:

> On Sat, Jul 15, 2017 at 11:05 PM, Peter Otten <__peter__ at web.de> wrote:
>> Matt Wheeler wrote:
>>
>>>> as the title says. has @ been used in projects?
>>
>> numpy, probably?
>>
>>> Strictly speaking, @ is not an operator.
>>
>> In other words it's not popular, not even widely known.
>>
>> Compare:
>>
>> $ python3.4 -c '__peter__ at web.de'
>>   File "<string>", line 1
>>     __peter__ at web.de
>>              ^
>> SyntaxError: invalid syntax
>> $ python3.5 -c '__peter__ at web.de'
>> Traceback (most recent call last):
>>   File "<string>", line 1, in <module>
>> NameError: name '__peter__' is not defined
>>
>> Starting with 3.5 my email address is valid Python syntax. Now I'm
>> waiting for the __peter__ builtin ;)
> 
> And you'll have to 'import web' too.
> 
> I've no idea what 'web.de' would be and what happens when you matmul it by
> you.
> 
> ChrisA

This is getting more complex than expected. Here's a prototype:

import builtins

def __peter__():
    class Provider:
        def __init__(self, name):
            self.name = name
        def __getattr__(self, name):
            return Provider(f"{self.name}.{name}")
        def __rmatmul__(self, user):
            assert user.email.endswith("@" + self.name)
            return user

    class User:
        def __init__(self, email):
            self.email = email
            user, at, site = email.partition("@")
            name = site.partition(".")[0]
            setattr(builtins, name, Provider(name))
        def __repr__(self):
            return self.email

    return User("__peter__ at web.de")

builtins.__peter__ = __peter__()

del __peter__

$ python3.7 -i web.py
>>> __peter__ at web.de
__peter__ at web.de

I'm sure you won't question the feature's usefulness after this. Future 
versions may send me an email or wipe your hard disk at my discretion...