Python 3 syntax error question

[Noah Hall]

On Sun, Jun 26, 2011 at 4:28 PM, rzed <rzantow at gmail.com> wrote:
> steve+comp.lang.python at pearwood.info wrote in
> news:4e074768$0$29982$c3e8da3$5496439d at news.astraweb.com:
>
>> rzed wrote:
>>
>>> I've tried to install PySVG in a Python 3 setting, and I get a
>>> few errors on the build. Most are easy to fix, but this one I
>>> can't explain or fix:
>>>
>>> <error>
>>> Traceback (most recent call last):
>>>   File "<stdin>", line 1, in <module>
>>>   File "builders.py", line 12, in <module>
>>>     from pysvg.shape import *
>>>   File "C:\Python32\lib\site-packages\pysvg\shape.py", line 91
>>>     def moveToPoint(self,(x,y)):
>>>                          ^
>>> SyntaxError: invalid syntax
>>> </error>
>>
>> Function signatures with automatic tuple-unpacking are no longer
>> allowed in Python3. So functions or methods like this:
>>
>> def moveToPoint(self,(x,y)):
>>
>> have to be re-written with the tuple unpacking moved into the
>> body of the function, e.g. something like this:
>>
>> def moveToPoint(self, x_y):
>>     x, y = x_y
>>
>>
>> Are you aware that you're trying to install a Python2 library
>> under Python3?
>>
>>
>
> Thank you all for your responses. Yes, I am aware of the version
> difference, but not of all the implications of that. I will run this
> through 2to3, but even without doing that, there are only about four
> syntax errors, and the others were obvious and easily corrected.
>
> There does not seem to be a Py3 version of this package. I was hoping
> to try it to see what broke. Well, I found out at least part of that,
> didn't I?
>
> I was not aware of the removal of tuple-unpacking. I expect there was
> some extensive conversation about that.
>
> As to 2to3, I have to say that:
>
> -def a(b, (c,d)):
> +def a(b, xxx_todo_changeme):
> +    (c,d) = xxx_todo_changeme
>
> ... is not terribly revealing if one is unaware of what about it
> needs changing. I know, I know: RTFM....

It means delete every line with a '-' and replace them with those next
to the '+'
Of course, if you read the doc, it'll give you lots of different
options, including writing to the file, so all you need to do is
change the variable names.