如何断言PyQt5信号的身份？

Question

我处于一种我想要断言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，涉及==，is和id()的三个比较分别都产生False，即它们未能断言左手和右手参数的身份。

有没有办法断言widget.clicked和signal引用相同的信号？

Answer 1

每次调用时都会创建作为实体的信号，因为它们代表不同的连接：

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，如果在同一信号和插槽之间连接100次，并且在发出信号时，插槽将被调用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

所以直接解决你的问题是不可能的，但我认为你的目标是区分哪个对象发出调用插槽的信号，因为你可能有几个对象连接到同一个插槽，如果有解决方案：

1. Using sender() method

如果插槽属于QObject（或从QObject派生的类作为小部件），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. Pass the object as an additional parameter

2.1 lambda function

---

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 function

---

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_())

---

在我的情况下，我更喜欢使用发送者，如果我可以使用它，然后functools.partial，最后使用lambda方法

Answer 2

试试吧：

import sys
from PyQt5.QtWidgets import QApplication, QPushButton

app = QApplication([])

def clickButton(w):
    # Check what you clicked here.                        # <-----
    return print(w.text())

widget  = QPushButton('Button 1')
widget.clicked.connect(lambda : clickButton(widget))

widget2 = QPushButton('Button 2')
widget2.clicked.connect(lambda : clickButton(widget2))

widget.setGeometry(300, 150, 100, 100)
widget.show()

widget2.setGeometry(450, 150, 100, 100)
widget2.show()

sys.exit(app.exec_())