[PyKDE] Printing empty QStrings

Phil Thompson phil at river-bank.demon.co.uk
Tue Oct 31 00:24:09 GMT 2000

Boudewijn Rempt wrote:
> Around version 0.10.1 QString started to return None when empty, instead
> of segfaulting. However, with the current version and Python 2.0, there
> is another problem: if you want to print an emtpy QString, you get the
> following:
> Python 2.0 (#1, Oct 28 2000, 11:41:22)
> [GCC egcs-2.91.66 19990314/Linux (egcs-1.1.2 release)] on linux2
> Type "copyright", "credits" or "license" for more information.
> >>> import qt
> >>> a = qt.QChar()
> >>> print a
> <qt.QChar instance at 0x81d71f4>
> >>> a=qt.QString()
> >>> print a
> Traceback (most recent call last):
>   File "<stdin>", line 1, in ?
>   File "/usr/local/lib/python2.0/site-packages/qt.py", line 898, in
> __str__
>     return str(self.sipThis)
> TypeError: __str__ returned non-string (type None)
> >>>
> I'm not sure what's right - returning None or repr(None) - but this
> used to work.

It's the intended behaviour - but I'm not convinced it is the right

The problem is how to differentiate between a null QString and an empty
QString. The choices are...

1. Keep it as it is and have an empty QString return a zero length
Python string and a null QString return None and trigger an exception.

2. Return a zero length Python string for both empty and null strings
(and use the appropriate QString methods if you really want to know if
it is empty or null).

3. Have a null QString return a Python string something like <null
QString at ...>.

4. Do (2) for str() and (3) for repr().

5. Do something else.



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