<div dir="ltr"><div class="gmail_default" style="font-family:tahoma,sans-serif">@Florian & @Phil,</div><div class="gmail_default" style="font-family:tahoma,sans-serif"><br></div><div class="gmail_default" style="font-family:tahoma,sans-serif">Your posts crossed with my last one above.</div><div class="gmail_default" style="font-family:tahoma,sans-serif"><br></div><div class="gmail_default" style="font-family:tahoma,sans-serif">Technically as I wrote there, one does <i>not</i> have to "go through Qt reading whether a "<span style="font-family:monospace,monospace">QObject *</span>" does or does not accept NULL/None, because it automatically <i>does</i>. As I wrote, if it does <i>not</i>, the correct Qt C++ declaration would have been "<span style="font-family:monospace,monospace">QObject &</span>", and that was up to the Qt people, not PyQt to guess.</div><div class="gmail_default" style="font-family:tahoma,sans-serif"><br></div><div class="gmail_default" style="font-family:tahoma,sans-serif">Having said that, I realise we are where we are. (Unless PyQt wants to change the declarations at the next release.) I am concerned about what I can do moving on. You guys have clarified to me that I am not "missing something" which would have solved this neatly. I now can declare <i>my own</i> function parameters/returns with <span style="font-family:monospace,monospace">Union</span>; I am stuck with where a PyQt function does not do so and so I will get a warning on my calling code, but at least I know where I am. So thank you all.<br></div></div><div class="gmail_extra"><br><div class="gmail_quote">On 22 November 2017 at 10:03, Florian Bruhin <span dir="ltr"><<a href="mailto:me@the-compiler.org" target="_blank">me@the-compiler.org</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><span class="">On Wed, Nov 22, 2017 at 09:38:21AM +0000, J Barchan wrote:<br>
> Thank you both, for the same solution. I had noticed the Union[QWidget,<br>
> None] construct and wondered if that was the only way/what I'm supposed to<br>
</span>> do in Python. But it raises two questions, *and only solves one of the two<br>
> problems*:<br>
<br>
As mentioned in an earlier reply, there's Optional[QWidget] which is a<br>
shorthand for that.<br>
<span class=""><br>
> 1. I am "surprised" at the need to do this from Python every time an object<br>
> might have value None. It's "cumbersome" compared to the way NULL/0 is<br>
> handled from C++, where it's always an acceptable value for any Object*<br>
> parameter/return value. Do you guys really write that for every place None<br>
> is acceptable?<br>
<br>
</span>Yes, and it's probably the more correct way, because the caller code *has* to<br>
deal with the value being None.<br>
<br>
> 2. The problem is unsolved where a *PyQt* function accepts/returns None.<br>
<span class="">> The second example I gave is calling QWidget.setParent(None). The<br>
> declaration of this in QtWidgets.pyi is:<br>
><br>
> def setParent(self, parent: 'QWidget') -> None:<br>
><br>
</span>> Following your solutions, this *ought* to have been:<br>
<span class="">><br>
> def setParent(self, parent: typing.Union['QWidget', None]) -> None:<br>
><br>
</span>> But the problem is that it *isn't* defined like that in the .pyi, and I<br>
<span class="">> can't help that. And it's not just that function, it's lots of others too<br>
> which accept or return None, so this issue keeps arising in my calling<br>
> code. Was it PyQt's job to recognise this and generate a different<br>
> declaration or what? Given where we are, I don't see any way of avoiding<br>
> the warning when calling such a PyQt function with None, do you?<br>
<br>
</span>Yes, PyQt should use Optional[QWidget] here. However, there's probably no way<br>
for PyQt to know where None is acceptable and where it isn't...<br>
<br>
FWIW last time I looked at PyQt's type definitions, they were mostly intended<br>
for IDE documentation, and not for typechecking - and mypy (probably the most<br>
widely used type checking tool) didn't like the files at all.<br>
<span class="HOEnZb"><font color="#888888"><br>
Florian<br>
<br>
--<br>
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</font></span></blockquote></div><br><br clear="all"><br>-- <br><div class="gmail_signature" data-smartmail="gmail_signature"><div dir="ltr"><div><div dir="ltr"><div><span style="font-family:tahoma,sans-serif">Kindest,</span></div><div><span style="font-family:tahoma,sans-serif">Jonathan</span></div></div></div></div></div>
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