Re: [gentoo-user] new machine : suddenly Python 3 appears

[David W Noon]

On Mon, 17 Sep 2012 17:17:47 -0400, Philip Webb wrote about Re:
[gentoo-user] new machine : suddenly Python 3 appears:

> 120917 Philip Webb wrote:
> > 120917 David W Noon wrote:
> >>    print('              {0}'.format(eval(expression)))
>
> That works properly with Python2 in this machine ;
> I'll check it with Python3 later in the new machine.

That *is* Python 3 syntax.  It is also accepted under recent releases
of Python 2.

> > 120917 Marc Joliet wrote:
> >>   print('              ',eval(expression))
>
> That does the calculation, but the output is wrongly formatted :
>
>   514 bin> pycalc1 2+3
>   ('              ', 5)

This is because Marc's code is syntactically invalid for Python 3.  It
is acceptable to Python 2, but does not do what you want; but it won't
work at all under Python 3.

It is clear that you have not taken my advice to use the -3 run-time
option in your hash-bang line.  At the risk of blowing my own trumpet,
that was *extremely sound* advice; you should really take it.  It would
have revealed the problems with the above code during the Python
interpreter's initial scan of the code.  I'll repeat it:
    !#/usr/bin/python2 -3
This will perform a Python 3 syntax check, even under Python 2.  It
will identify any going-forward issues for your Python script(s).
-- 
Regards,

Dave  [RLU #314465]
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dwnoon@××××××××.com (David W Noon)
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