[Cython] from __future__ import ...

[Stefan Behnel]

Hi Lisandro,

please read what I post. You've been stating repeatedly that your experience
with Unicode is limited, and I think I have told you a lot of what I know
about the subject. I appreciate discussion, but please consider that I might
have more reasons for my opinions about the subject than I state in each
single post.


Lisandro Dalcin wrote:
> On 5/16/08, Stefan Behnel <stefan_ml at behnel.de> wrote:
>> The thing is that if you write
>>
>>     getattr(o, u"attr")
>>
>>  in Cython, it will work in both Py2 and Py3. However,
>>
>>     getattr(o, "attr")
>>
>>  will only work in Py2, unless you do the future import.
> 
> Stefan, I understood that one of the traget of Cython is to
> efficiently compile Python code. Please note that
> 
> getattr(o, u"attr")
> 
> is not valid Python 3 code at all !!

That's why I said "in Cython".


> You are proposing that if I do "def foo(): ..." the the identifier
> 'foo' will be implicitely treated as unicode for Py3,

Sure. You didn't state in your source that you wanted the identifier name to
be a byte string, did you? (which was obviously because Python doesn't allow
you to do that).


> but a string literal "abc" do not !!.

Because the syntax of Python2, which Cython currently implements, dictates
that "abc" is a byte string. This is explicit in Python2, as the unicode
string would be u"abc".

The difference between identifiers and strings is that one is a name and the
other is a piece of data. The language can do whatever it likes with the names
(it can even strip them from the compiled result completely), but it must
*never* corrupt data.

Py3 has come a long way since the initial Unicode support in Py 2.0, almost
eight years back. We shouldn't throw all lessons learned away and think we can
do better.

Stefan