python - 如何声明PyQt5信号的身份？

我处于要断言PyQt5信号身份的情况。具体来说，我想检查来自给定clicked对象的QPushButton信号是否与存储在名为signal的变量中的信号相同。以下代码段说明了这种情况：

from PyQt5.QtWidgets import QApplication, QPushButton

app = QApplication([])
widget = QPushButton()
signal = widget.clicked

widget.clicked == signal
Out[1]: False

widget.clicked is signal
Out[2]: False

id(widget.clicked) == id(signal)
Out[3]: False

如图所示，分别涉及==，is和id()的三个比较均产生False，即它们未能断定左手参数和右手参数的身份。

有什么方法可以断言widget.clicked和signal引用相同的信号吗？

最佳答案

信号作为实体会在您每次调用它时创建，因为它们表示不同的连接：

In [1]: import sys

In [2]: from PyQt5 import QtWidgets

In [3]: app = QtWidgets.QApplication(sys.argv)

In [4]: button = QtWidgets.QPushButton()

In [5]: id(button.clicked)
Out[5]: 140150155639464

In [6]: id(button.clicked)
Out[6]: 140150154507528

In [7]: id(button.clicked)
Out[7]: 140150155640184

In [8]: id(button.clicked)
Out[8]: 140150155640504

In [9]: id(button.clicked)
Out[9]: 140150154510128

In [10]: id(button.clicked)
Out[10]: 140149427454320

因此，如果您在同一信号和插槽之间连接100次，并且在发射信号时，该插槽将被称为100次：

import sys
from PyQt5 import QtCore, QtWidgets

def foo():
    print("clicked")

if __name__ == '__main__':

    app = QtWidgets.QApplication(sys.argv)
    button = QtWidgets.QPushButton("Press me")
    button.show()
    for _ in range(10):
        button.clicked.connect(foo)
    # the click is emulated
    QtCore.QTimer.singleShot(1000, lambda: button.animateClick(500))
    QtCore.QTimer.singleShot(2000, app.quit)
    sys.exit(app.exec_())

输出：

clicked
clicked
clicked
clicked
clicked
clicked
clicked
clicked
clicked
clicked

因此，不可能直接解决您的问题，但是我认为您的目标是区分哪个对象发出了调用插槽的信号，因为您可能有多个对象连接到同一插槽，如果有解决方案，则可以这样做：

1.使用sender()方法

如果插槽属于QObject（或作为QWidget派生自QObject的类），则可以使用sender方法获取发出信号的对象。

import sys
from PyQt5 import QtCore, QtWidgets

class Widget(QtWidgets.QWidget):
    def __init__(self, parent=None):
        super(Widget, self).__init__(parent)

        self.button_1 = QtWidgets.QPushButton("button 1")
        self.button_1.clicked.connect(self.foo)
        self.button_2 = QtWidgets.QPushButton("button 2")
        self.button_2.clicked.connect(self.foo)
        self.button_3 = QtWidgets.QPushButton("button 3")
        self.button_3.clicked.connect(self.foo)

        lay = QtWidgets.QVBoxLayout(self)
        lay.addWidget(self.button_1)
        lay.addWidget(self.button_2)
        lay.addWidget(self.button_3)

    @QtCore.pyqtSlot()
    def foo(self):
        button = self.sender()
        if button is self.button_1:
            print("button_1")
        elif button is self.button_2:
            print("button_2")
        elif button is self.button_3:
            print("button_3")

if __name__ == '__main__':

    app = QtWidgets.QApplication(sys.argv)
    w = Widget()
    w.show()
    sys.exit(app.exec_())

2.将对象作为附加参数传递

2.1 Lambda函数

import sys
from PyQt5 import QtCore, QtWidgets

class Widget(QtWidgets.QWidget):
    def __init__(self, parent=None):
        super(Widget, self).__init__(parent)

        self.button_1 = QtWidgets.QPushButton("button 1")
        self.button_1.clicked.connect(lambda *args, b=self.button_1 : self.foo(b))
        self.button_2 = QtWidgets.QPushButton("button 2")
        self.button_2.clicked.connect(lambda *args, b=self.button_2 : self.foo(b))
        self.button_3 = QtWidgets.QPushButton("button 3")
        self.button_3.clicked.connect(lambda *args, b=self.button_3 : self.foo(b))

        lay = QtWidgets.QVBoxLayout(self)
        lay.addWidget(self.button_1)
        lay.addWidget(self.button_2)
        lay.addWidget(self.button_3)

    def foo(self, button):
        if button is self.button_1:
            print("button_1")
        elif button is self.button_2:
            print("button_2")
        elif button is self.button_3:
            print("button_3")

if __name__ == '__main__':

    app = QtWidgets.QApplication(sys.argv)
    w = Widget()
    w.show()
    sys.exit(app.exec_())

2.1 functools.partial函数

import sys
from PyQt5 import QtCore, QtWidgets
from functools import partial

class Widget(QtWidgets.QWidget):
    def __init__(self, parent=None):
        super(Widget, self).__init__(parent)

        self.button_1 = QtWidgets.QPushButton("button 1")
        self.button_1.clicked.connect(partial(self.foo, self.button_1))
        self.button_2 = QtWidgets.QPushButton("button 2")
        self.button_2.clicked.connect(partial(self.foo, self.button_2))
        self.button_3 = QtWidgets.QPushButton("button 3")
        self.button_3.clicked.connect(partial(self.foo, self.button_3))

        lay = QtWidgets.QVBoxLayout(self)
        lay.addWidget(self.button_1)
        lay.addWidget(self.button_2)
        lay.addWidget(self.button_3)

    def foo(self, button):
        if button is self.button_1:
            print("button_1")
        elif button is self.button_2:
            print("button_2")
        elif button is self.button_3:
            print("button_3")

if __name__ == '__main__':

    app = QtWidgets.QApplication(sys.argv)
    w = Widget()
    w.show()
    sys.exit(app.exec_())

就我而言，如果可以使用，我更喜欢使用sender，然后使用functools.partial和lambda方法

关于python - 如何声明PyQt5信号的身份？，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/54712203/