问题:当在插槽中引发异常(由信号调用)时,异常似乎不会像往常一样通过Python调用堆栈传播.在下面的示例代码中调用:
> on_raise_without_signal():将按预期处理异常.
> on_raise_with_signal():将打印异常,然后意外地从else块打印成功消息.
问题:在插槽中引发异常后,异常处理的原因是什么?是信号/插槽的PySide Qt包装的一些实现细节/限制吗?有什么要阅读的文档吗?
PS:当我在实现QAbstractTableModels虚拟方法insertRows()和removeRows()时使用try / except / else / finally时得到令人惊讶的结果时,我最初遇到了该主题.
# -*- coding: utf-8 -*-
"""Testing exception handling in PySide slots."""
from __future__ import unicode_literals, print_function, division
import logging
import sys
from PySide import QtCore
from PySide import QtGui
logging.basicConfig(level=logging.DEBUG)
logger = logging.getLogger(__name__)
class ExceptionTestWidget(QtGui.QWidget):
raise_exception = QtCore.Signal()
def __init__(self, *args, **kwargs):
super(ExceptionTestWidget, self).__init__(*args, **kwargs)
self.raise_exception.connect(self.slot_raise_exception)
layout = QtGui.QVBoxLayout()
self.setLayout(layout)
# button to invoke handler that handles raised exception as expected
btn_raise_without_signal = QtGui.QPushButton("Raise without signal")
btn_raise_without_signal.clicked.connect(self.on_raise_without_signal)
layout.addWidget(btn_raise_without_signal)
# button to invoke handler that handles raised exception via signal unexpectedly
btn_raise_with_signal = QtGui.QPushButton("Raise with signal")
btn_raise_with_signal.clicked.connect(self.on_raise_with_signal)
layout.addWidget(btn_raise_with_signal)
def slot_raise_exception(self):
raise ValueError("ValueError on purpose")
def on_raise_without_signal(self):
"""Call function that raises exception directly."""
try:
self.slot_raise_exception()
except ValueError as exception_instance:
logger.error("{}".format(exception_instance))
else:
logger.info("on_raise_without_signal() executed successfully")
def on_raise_with_signal(self):
"""Call slot that raises exception via signal."""
try:
self.raise_exception.emit()
except ValueError as exception_instance:
logger.error("{}".format(exception_instance))
else:
logger.info("on_raise_with_signal() executed successfully")
if (__name__ == "__main__"):
application = QtGui.QApplication(sys.argv)
widget = ExceptionTestWidget()
widget.show()
sys.exit(application.exec_())