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FormWidget fails to get a date or datetime value with PySide2 #18958
Description
Bug report
Bug summary
matplotlib.backends.qt_editor._formlayout.FormWidget.get() converts values of date and datetime fields into python datetime.date and datetime.datetime objects using toPyDate() and toPyDateTime() methods. These exist only in PyQt5; in PySide2 the corresponding functions are called toPython().
One way to fix this is to patch matplotlib.backends.qt_compat._setup_pyqt5() by adding the following lines under if QT_API == QT_API_PYSIDE2:
...
elif QT_API == QT_API_PYSIDE2:
from PySide2 import QtCore, QtGui, QtWidgets, __version__
import shiboken2
def _isdeleted(obj): return not shiboken2.isValid(obj)
QtWidgets.QDateTime.toPyDateTime = QtWidgets.QDateTime.toPython # fix QDatetime
QtWidgets.QDate.toPyDate = QtWidgets.QDate.toPython # fix QDate
else:
....Code for reproduction
from datetime import datetime
from PySide2.QtWidgets import QApplication
from matplotlib.backends.qt_editor._formlayout import FormWidget
QApplication()
widget = FormWidget([("Date time", datetime(year=2020, month=11, day=16))])
widget.setup()
values = widget.get()Actual outcome
Traceback (most recent call last):
File "formwidget.py", line 8, in <module>
values = widget.get()
File "lib\site-packages\matplotlib\backends\qt_editor\_formlayout.py", line 346, in get
value = field.dateTime().toPyDateTime()
AttributeError: 'PySide2.QtCore.QDateTime' object has no attribute 'toPyDateTime'
Expected outcome
No output, especially no tracebacks.
Matplotlib version
- Operating system: Windows 10
- Matplotlib version: 3.3.0 (the bug seems to be in
mastertoo) - Matplotlib backend (
print(matplotlib.get_backend())): qt5agg - Python version: 3.7.6
- Jupyter version (if applicable):
- Other libraries: PySide2
Activity
anntzer commentedon Nov 16, 2020
Thanks for the report; I don't think we should be patching the PySide2 API (it is what it is); an alternate solution would be along the lines of
However note that
_formlayoutis explicitly private and not suitable for general consumption; we reserve the right to change the module without notice (for example, given that we don't actually use this feature internally, we could certainly decide to "fix" this by just deleting the whole feature). Consider using the PyPI package (https://pypi.org/project/formlayout/) instead.OTOH this may be a good opportunity to fix the qt editor's behavior wrt units (currently it doesn't handle them at all...).
soininen commentedon Nov 16, 2020
Thanks for the prompt answer. The issue actually boils down to the figure options editor: we are using date time values on the x axis extensively but the editor's axis limits shows date times as floats making adjustments difficult. I am monkey patching
matplotlib.backends.qt_editor.figureoptions.figure_editto convert the units to correct input widgets which made me discover the issue at hand. Fixing the editor to handle units correctly would indeed be more 'correct' approach.soininen commentedon Dec 7, 2020
As discussed above, the real fix for my problem would be to make Qt backend's figure options dialog to handle units properly.