python - PyQt5在两个类之间传递参数: lambda vs partial

Question

我正在尝试在两个 PyQt5 类之间传递参数。我使用了三种方法:

1. 使用 lambda 函数。
2. 包装函数(类似于 lambda 函数)。
3. partial来自functools模块。

在下面的示例中，我有两个窗口:

• 主窗口有 QLineEdit mw_line_edit和一个 QPushButton mw_open_new_dialog_button .
• 对话框:有一个 QLineEdit line_edit和 aQPushButton push_button 。

当我点击按钮push_button时，我想让它插入line_edit的内容至mw_line_edit .

这是一个最小的例子:

import sys
from functools import partial

from PyQt5 import QtWidgets, QtGui, QtCore


class MainWindow(QtWidgets.QMainWindow):
    def __init__(self, parent=None):
        super(MainWindow, self).__init__(parent)
        self.central_widget = QtWidgets.QWidget(self)
        self.setCentralWidget(self.central_widget)
        self.mw_open_new_dialog_button = QtWidgets.QPushButton('Open New dialog', self)
        self.mw_line_edit = QtWidgets.QLineEdit(self)
        self.hlayout = QtWidgets.QHBoxLayout(self)
        self.hlayout.addWidget(self.mw_open_new_dialog_button)
        self.hlayout.addWidget(self.mw_line_edit)
        self.central_widget.setLayout(self.hlayout)

        self.mw_open_new_dialog_button.clicked.connect(self.open_new_dialog)


    def open_new_dialog(self):
        self.dlg = Dialog()
        #self.dlg.clicked.connect(partial(self.write_something, self.dlg.line_edit.text())) # <<<<<<< This does not work
        self.dlg.clicked.connect(lambda: self.write_something(self.dlg.line_edit.text())) # this works
        #self.dlg.clicked.connect(self.wrapper(self.dlg.line_edit.text()))# <<<<<<<<<<This does not work 
        self.dlg.exec()

    @QtCore.pyqtSlot()
    def write_something(self, text):
        self.mw_line_edit.setText(text)

    def wrapper(self, text):
        return lambda: self.write_something(text)



class Dialog(QtWidgets.QDialog):

    clicked = QtCore.pyqtSignal()
    def __init__(self, parent=None):
        super(QtWidgets.QDialog, self).__init__(parent)
        self.hlayout = QtWidgets.QHBoxLayout(self)
        self.line_edit = QtWidgets.QLineEdit(self)
        self.push_button = QtWidgets.QPushButton('Click me', self)
        self.hlayout.addWidget(self.line_edit)
        self.hlayout.addWidget(self.push_button)
        self.label = QtWidgets.QLabel('I am a Qlabel', self)
        self.hlayout.addWidget(self.label)
        self.setLayout(self.hlayout)
        self.push_button.clicked.connect(self.clicked)

    def write_something(self, text):
        print(text)



app = QtWidgets.QApplication(sys.argv)

main_window = MainWindow()
main_window.show()
sys.exit(app.exec())

正如您在注释行中看到的，只有以下方法有效:

self.dlg.clicked.connect(lambda: self.write_something(self.dlg.line_edit.text()))

为什么其他两个不起作用，即:

self.dlg.clicked.connect(partial(self.write_something, self.dlg.line_edit.text())) # <<<<<<< This does not work

self.dlg.clicked.connect(self.wrapper(self.dlg.line_edit.text()))# <<<<<<<<<<This does not work

谢谢

Answer 1

1) functools.partial()

您要传递给partial的参数是什么？您当时正在传递方法write_something和self.dlg.line_edit的文本连接已建立。

该文本的值是多少？它是一个空字符串，这解释了失败。

这种情况有什么解决方案吗？是的，不传递文本，而是传递QLineEdit，并在方法write_something中获取文本并将其设置在另一个QLineEdit中:

def open_new_dialog(self):
    self.dlg = Dialog()
    self.dlg.clicked.connect(partial(self.write_something, self.dlg.line_edit))
    self.dlg.exec()

def write_something(self, le):
    self.mw_line_edit.setText(le.text())

2) 包装器

这是同样的问题，您正在传递连接时的空文本

有什么解决办法吗？有，和上一个一样的解决办法。

def open_new_dialog(self):
    self.dlg = Dialog()
    self.dlg.clicked.connect(self.wrapper(self.dlg.line_edit))
    self.dlg.exec()

def write_something(self, text):
    self.mw_line_edit.setText(text)

def wrapper(self, line):
    return lambda: self.write_something(line.text())

<小时/>

会有一个干净的解决方案吗？是的，创建一个在您点击时传输文本的信号。

from PyQt5 import QtWidgets, QtGui, QtCore

class MainWindow(QtWidgets.QMainWindow):
    def __init__(self, parent=None):
        super(MainWindow, self).__init__(parent)
        central_widget = QtWidgets.QWidget()
        self.setCentralWidget(central_widget)
        self.mw_open_new_dialog_button = QtWidgets.QPushButton('Open New dialog')
        self.mw_line_edit = QtWidgets.QLineEdit()
        hlayout = QtWidgets.QHBoxLayout(central_widget)
        hlayout.addWidget(self.mw_open_new_dialog_button)
        hlayout.addWidget(self.mw_line_edit)
        self.mw_open_new_dialog_button.clicked.connect(self.open_new_dialog)

    @QtCore.pyqtSlot()
    def open_new_dialog(self):
        self.dlg = Dialog()
        self.dlg.textSignal.connect(self.mw_line_edit.setText)
        self.dlg.exec()

class Dialog(QtWidgets.QDialog):
    textSignal = QtCore.pyqtSignal(str)

    def __init__(self, parent=None):
        super(QtWidgets.QDialog, self).__init__(parent)
        hlayout = QtWidgets.QHBoxLayout(self)
        self.line_edit = QtWidgets.QLineEdit()
        self.push_button = QtWidgets.QPushButton('Click me')
        hlayout.addWidget(self.line_edit)
        hlayout.addWidget(self.push_button)
        self.label = QtWidgets.QLabel('I am a Qlabel')
        hlayout.addWidget(self.label)
        self.push_button.clicked.connect(self.sendText)

    @QtCore.pyqtSlot()
    def sendText(self):
        self.textSignal.emit(self.line_edit.text())

if __name__ == '__main__':
    import sys
    app = QtWidgets.QApplication(sys.argv)
    main_window = MainWindow()
    main_window.show()
    sys.exit(app.exec())