Ah ha! I read in
/pipermail/pyqt/2016-April/037326.html:
>>>>* I am currently updating QGIS to PyQt5 (and Qt5 and Python3)>>>>
Since this update, NULL QVariant strings are converted to empty
strings '' and all numbers to 0 when converted from C++ to python
objects.*
And that is exactly what I am experiencing: the string-NULL is giving me
empty string and the int-NULL is giving me 0. So isn't this a PyQt issue I
am seeing after all??
On 3 May 2018 at 14:50, J Barchan <jnbarchan at gmail.com> wrote:
> Hang on. This is an area I do not understand, doubtless you do.
>> The C++ QSqlQueryModel::data() method is supposed to return a QVariant.
> Am I maybe losing the QVariant-ness when I write my own PyQt overload
> which returns the base method's result, because Python-esque conversion is
> going on?
>> I'm trying to understand http://pyqt.sourceforge.net/
> Docs/PyQt5/pyqt_qvariant.html, but I don't really. I do note:
> > There is no obvious way to represent a null QVariant
> <http://pyqt.sourceforge.net/Docs/PyQt5/api/QtCore/qvariant.html#PyQt5-QtCore-QVariant>
> as a standard Python object.
>> Is there a connection between this and the fact that it goes wrong when
> the value it should be returning is the NULL returned from the SQL query?
>> On 3 May 2018 at 13:55, J Barchan <jnbarchan at gmail.com> wrote:
>>>>>>> On 3 May 2018 at 13:05, Phil Thompson <phil at riverbankcomputing.com>
>> wrote:
>>>>> On 3 May 2018, at 12:25 pm, J Barchan <jnbarchan at gmail.com> wrote:
>>> >
>>> > 鈥嬧��
>>> > I am finding (in PyQt 5.7 at least) that sub-classing QSqlQueryModel
>>> and overriding its data() method produces an incorrect result when the
>>> value retrieved from a MySQL database is NULL.鈥�
>>> >
>>> > Full details are in https://forum.qt.io/topic/9036
>>> 3/inexplicable-qsqlquerymodel-handling-of-null-value, and particularly
>>> post # https://forum.qt.io/topic/90363/inexplicable-qsqlquerymodel-
>>> handling-of-null-value. Nobody has tried it in C++ for me to date to
>>> verify, but I'm suspecting this might be a PyQt bug?
>>> >
>>> > Briefly:
>>> > My SELECT query returns a column which is NULLable, and has NULL as
>>> its value. Where I expect "blank" as the end value, I actually get, for
>>> example, 0 if the column type is int or '' if the type is string, etc.
>>> >
>>> > This is when I sub-class QSqlQueryModel. If all I have is:
>>> > class DBQueryModel(QtSql.QSqlQueryModel):
>>> > def __init__(self, parent=None):
>>> > super().__init__(parent)
>>> > I get the "NULL"/"blank". However, as soon as I add just:
>>> > def data(self, index: QtCore.QModelIndex, role=QtCore.Qt.DisplayRole)
>>> -> typing.Any:
>>> > return super().data(index, role)
>>> > I get those values instead of NULL.
>>> >
>>> > Note that my override is based on the Qt definition of the method at
>>> http://doc.qt.io/qt-5/qsqlquerymodel.html#data:
>>> > QVariant QSqlQueryModel::data(const QModelIndex &item, int role =
>>> Qt::DisplayRole) const
>>> >
>>> > Note that the default for role is Qt::DisplayRole. However, in
>>> QtSql.py I see:
>>> > def data(self, QModelIndex, role=None): # real signature unknown;
>>> restored from __doc__
>>> > """ data(self, QModelIndex, role: int = Qt.DisplayRole) -> Any """
>>> > pass
>>> > You will notice that the comment shows the default should be
>>> Qt.DisplayRole, but the declaration defaults it to None instead.
>>>>>> What is QtSql.py?
>>>>>> If you want to know the signature of a method pss it to help().
>>>>>> > I don't know enough to be sure, but would that be the underlying cause
>>> of the unexpected behaviour?
>>> >
>>> > FWIW, I have tried making my override be:
>>> > def data(self, index: QtCore.QModelIndex, role=None)
>>> > instead, but same bad behaviour.
>>> >
>>> > 1. Is this indeed a bug in PyQt, and the cause of my issue?
>>>>>> No and no.
>>>>>> > 2. If so, I presume you (Phil!) will be kind enough to fix. However,
>>> for my part I am stuck with PyQt 5.7 for the foreseeable future. If the
>>> fix is indeed to change code in the latest/next release, is there anything
>>> I can do in existing code (my override) to make it work in 5.7, as a
>>> workaround? (in real code I need the override, as I do other processing)
>>> >
>>> > My coding has come to halt as I cannot proceed without a fix. So I
>>> should be obliged for any early response as to whether this is the cause of
>>> my woes. I do realise PyQt support/fixes are quite voluntary, and so thank
>>> whoever in advance!
>>>>>> Phil
>>>>>> 鈥婩or QtSql.py:鈥�
>>>> 鈥婬mm鈥�, I had not realised. I use PyCharm as my IDE. From there, while I
>> am coding, I can click on anything PyQt and ask for "Go to
>> definition/declaration". The editor then 9in this case) opens me up into a
>> file named QtSql.py, showing me in this case [extract]:
>>>> class QSqlQueryModel(__PyQt5_QtCore.QAbstractTableModel):
>>>>>> ...
>>>>>> def columnCount(self, parent=None, *args, **kwargs): # real signature unknown; NOTE: unreliably restored from __doc__
>>> """ columnCount(self, parent: QModelIndex = QModelIndex()) -> int """
>>> pass
>>>>>> def data(self, QModelIndex, role=None): # real signature unknown; restored from __doc__
>>> """ data(self, QModelIndex, role: int = Qt.DisplayRole) -> Any """
>>> pass
>>>>>> def endInsertColumns(self): # real signature unknown; restored from __doc__
>>> """ endInsertColumns(self) """
>>> pass
>>>>>>>> etc. I had *assumed* this was a file supplied with PyQt. I guess now
>> it's "generated on the fly" by PyCharm (I see its path is in a PyCharm
>> temporary directory). At other times, it might open, say,
>> /usr/lib/python3/dist-packages/PyQt5/QtCore.pyi, which I think is a file
>> you supply. Oh, at the head of this QtSql.py I see:
>>>> # encoding: utf-8
>> # module PyQt5.QtSql
>> # from /usr/lib/python3/dist-packages/PyQt5/QtSql.cpython-35m-x86_64-linux-gnu.so
>> # by generator 1.145
>> # no doc
>>>>>> 鈥媃ou'll probably understand all this better than I!鈥�
>>>>>>>> 鈥婩or my problem:鈥�
>>>> I think I now understand better why it's not a PyQt method definition
>> issue.
>>>> However, from the linked Qt forum discussion, I'm stuck between a rock &
>> a hard place, because the only help I'm getting is that it might be a PyQt
>> issue. I do not have C++ to try that out. So, I wonder if I might ask you
>> if you can make any suggestion as to the cause, even if it is not a PyQt
>> issue, given that you are familiar with Qt at least?
>>>> To summarise my problem as briefly as possible:
>>>> 1.
>> I start with:
>>>> model = QtSql.QSqlQueryModel(self)
>> model.setQuery("SELECT LandlordNo, SMTPAccountId FROM landlords WHERE SMTPAccountId IS NULL")
>>>> # or plain "SELECT NULL AS SMTPAccountId", to eliminate anything about the column definition being an issue
>>>> rowCount = model.rowCount()
>> if rowCount > 0:
>> rec = model.record(0)
>> field = rec.field("SMTPAccountId")
>> isn = field.isNull()
>>>> SMTPAccointId returns NULL from MySQL. *At this point field.isNull()
>> correctly returns True.*
>>>> 2.
>> I sub-class QSqlQueryModel, and use that, with quite simply, exactly:
>>>> class DBQueryModel(QtSql.QSqlQueryModel):
>> def __init__(self, parent=None):
>> super().__init__(parent)
>>>> and use that sub-class in place of QSqlQueryModel: model =
>> DBQueryModel(self)
>> 鈥�*And it this point 鈥媝oint field.isNull() *still* correctly returns
>> True.*
>>>> 3.
>> Then I add *just exactly this* to my sub-class:
>>>> def data(self, index: QtCore.QModelIndex, role=QtCore.Qt.DisplayRole) -> typing.Any:
>> return super().data(index, role)
>>>> (I've also tried role=None) You can see that simply calls the base class
>> method. *But now field.isNull() returns False!!* The application sees 0
>> instead of NULL for the value (SMTPAccountId is declared INT NULL), or ''
>> if I use SELECT NULL AS SMTPAccountId so it counts as string.
>>>>>> This leaves me completely stumped. I have no idea where the problem is
>> (there shouldn't be a problem!). I have to sub-class the data() method
>> for other purposes, but then it handles NULL (only) incorrectly.
>>>> Would you have any idea what is going on here? My thanks in advance.
>>>>>> --
>> Kindest,
>> Jonathan
>>>>>> --
> Kindest,
> Jonathan
>
--
Kindest,
Jonathan
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‘She has never mentioned her father to me. Was he—well, the sort of man whom the County Club would not have blackballed?’ "We walked by the side of our teams or behind the wagons, we slept on the ground at night, we did our own cooking, we washed our knives by sticking them into the ground rapidly a few times, and we washed our plates with sand and wisps of grass. When we stopped, we arranged our wagons in a circle, and thus formed a 'corral,' or yard, where we drove our oxen to yoke them up. And the corral was often very useful as a fort, or camp, for defending ourselves against the Indians. Do you see that little hollow down there?" he asked, pointing to a depression in the ground a short distance to the right of the train. "Well, in that hollow our wagon-train was kept three days and nights by the Indians. Three days and nights they stayed around, and made several attacks. Two of our men were killed and three were wounded by their arrows, and others had narrow escapes. One arrow hit me on the throat, but I was saved by the knot of my neckerchief, and the point only tore the skin a little. Since that time I have always had a fondness for large neckties. I don't know how many of the Indians we killed, as they carried off their dead and wounded, to save them from being scalped. Next to getting the scalps of their enemies, the most important thing with the Indians is to save their own. We had several fights during our journey, but that one was the worst. Once a little party of us were surrounded in a small 'wallow,' and had a tough time to defend ourselves successfully. Luckily for us, the Indians had no fire-arms then, and their bows and arrows were no match for our rifles. Nowadays they are well armed, but there are[Pg 41] not so many of them, and they are not inclined to trouble the railway trains. They used to do a great deal of mischief in the old times, and many a poor fellow has been killed by them." As dusk came on nearly the whole population of Maastricht, with all their temporary guests, formed an endless procession and went to invoke God's mercy by the Virgin Mary's intercession. They went to Our Lady's Church, in which stands the miraculous statue of Sancta Maria Stella Maris. The procession filled all the principal streets and squares of the town. I took my stand at the corner of the Vrijthof, where all marched past me, men, women, and children, all praying aloud, with loud voices beseeching: "Our Lady, Star of the Sea, pray for us ... pray for us ... pray for us ...!" It had not occurred to her for some hours after Mrs. Campbell had told her of Landor's death that she was free now to give herself to Cairness. She had gasped, indeed, when she did remember it, and had put the thought away, angrily and self-reproachfully. But it returned now, and she felt that she might cling to it. She had been grateful, and she had been faithful, too.[Pg 286] She remembered only that Landor had been kind to her, and forgot that for the last two years she had borne with much harsh coldness, and with a sort of contempt which she felt in her unanalyzing mind to have been entirely unmerited. Gradually she raised herself until she sat quite erect by the side of the mound, the old exultation of her half-wild girlhood shining in her face as she planned the future, which only a few minutes before had seemed so hopeless. After he had gloated over Sergeant Ramsey, Shorty got his men into the road ready to start. Si placed himself in front of the squad and deliberately loaded his musket in their sight. Shorty took his place in the rear, and gave out: The groups about each gun thinned out, as the shrieking fragments of shell mowed down man after man, but the rapidity of the fire did not slacken in the least. One of the Lieutenants turned and motioned with his saber to the riders seated on their horses in the line of limbers under the cover of the slope. One rider sprang from each team and ran up to take the place of men who had fallen. "As long as there's men and women in the world, the men 'ull be top and the women bottom." Then, in the house, the little girls were useful. Mrs. Backfield was not so energetic as she used to be. She had never been a robust woman, and though her husband's care had kept her well and strong, her frame was not equal to Reuben's demands; after fourteen years' hard labour, she suffered from rheumatism, which though seldom acute, was inclined to make her stiff and slow. It was here that Caro and Tilly came in, and Reuben began to appreciate his girls. After all, girls were needed in a house—and as for young men and marriage, their father could easily see that such follies did not spoil their usefulness or take them from him. Caro and Tilly helped their grandmother in all sorts of ways—they dusted, they watched pots, they shelled peas and peeled potatoes, they darned house-linen, they could even make a bed between them. HoME一级毛片视频免费公开
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