Beginner needs advice

[Thorsten Kampe]

* Thomas Rachel (Sat, 28 May 2011 07:06:53 +0200)
> Am 27.05.2011 17:52 schrieb Steven D'Aprano:
> > On Fri, 27 May 2011 09:40:53 -0500, harrismh777 wrote:
> >> 3.x is completely incompatible with 2.x (some call it a dialect,
> >> but that is a lie).
> >
> > "Completely incompatible"? A "lie"?
> 
> Hard word, but it is true. Many things can and will fall on your feet
> when moving.

I think we should stop talking about (in)compatability because everyone 
seems to associate something different with that term (incompatible = 
"no Python2 to code will run with Python3", "not all Python2 code will 
run with Python3").

The question is: if you want (or have) to run your code under Python3, 
how likely is that it will run unmodified? My experience is: unless the 
code is especially written with Python3 compatability or just a short 
snippet, it's actually quite unlikely that it will run.

I modified three programs/modules (none of them written with Python3 in 
mind - I was thinking that Python 3000 would come out some day after 
Perl 6, PHP 6 and GNU Hurd; how could I know that the Python developers 
actually mean business?)

One is a tool box kind of module. I had to insert lots of "list()" and 
add a complete function that would deal with the different behaviour of 
"sort". Probably easy to find the problems if you have extensive unit 
tests but without it was a tedious nightmare.

The second a kind of script template. gettext.install has no "unicode = 
True". Easy fix but I wondered why Python 3 does not ignore the keyword 
simply.

The third, a more real world complete application using PyQt. Took me 
about a day to fix. The problem was not just with the code but also with 
the tools (pyuic4, pyrcc4). Without the PyQt mailing list this wouldn't 
have been possible. Still: a complete workday (or even more) for 150 
lines of code.


Thorsten