[Python-Dev] Challenge about print >> None

[M.-A. Lemburg]

Vladimir Marangozov wrote:
> 
> Seems like people are very surprised to see "print >> None" defaulting
> to "print >> sys.stderr". I must confess that now that I'm looking at
> it and after reading the PEP, this change lacks some argumentation.

According to the PEP it defaults to sys.stdout with the effect of
working just like the plain old "print" statement.

> In Python, this form surely looks & feels like the Unix cat /dev/null,
> that is, since None doesn't have a 'write' method, the print statement
> is expected to either raise an exception or be specialized for None to mean
> "the print statement has no effect". The deliberate choice of sys.stderr
> is not obvious.
> 
> I understand that Guido wanted to say "print >> None, args == print args"
> and simplify the script logic, but using None in this case seems like a
> bad spelling <wink>.
> 
> I have certainly carefully avoided any debates on the issue as I don't
> see myself using this feature any time soon, but when I see on c.l.py
> reactions of surprise on weakly argumented/documented features and I
> kind of feel the same way, I'd better ask for more arguments here myself.

+1

I'd opt for raising an exception instead of magically using
sys.stdout just to avoid two lines of explicit defaulting to
sys.stdout (see the example in the PEP).

BTW, I noted that the PEP pages on SF are not up-to-date. The
PEP 214 doesn't have the comments which Guido added in support
of the proposal.

-- 
Marc-Andre Lemburg
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