PyQt5 父窗口和子窗口信息通信

（1） 父窗口->子窗口
父窗口的__init__函数里面先创建子窗口实例，然后再通过某个控件的信号（例如button的clicked信号）绑定某个槽（slot），槽函数直接对子窗口的控件进行操作

（2）子窗口->父窗口（参考：https://blog.csdn.net/huang_6/article/details/106788420）
这种方式比较麻烦一点，子窗口中定义一个信号（参数中指定信号的类型和数量，例如_signal = pyqtSignal(str,int)，然后通过槽函数释放该信号，最后在主窗口上将该信号绑定到槽函数进而获取子窗口传递的消息。

具体例子如下：

# -*- coding: utf-8 -*-
"""
Created on Sun May 30 22:25:19 2021

@author: Wenqing Zhou ([email protected])
@github: https://github.com/ouening
"""

import sys
from PyQt5.QtWidgets import *
from PyQt5.QtCore import *
from random import randint
class AnotherWindow(QWidget):
    """
    This "window" is a QWidget. If it has no parent, it 
    will appear as a free-floating window.
    """
    _signal = pyqtSignal(str)
    def __init__(self):

        super().__init__()
        layout = QVBoxLayout()
        self.label = QLabel("Another Window % d" % randint(0, 100))

        self.qline = QLineEdit("send_data")
        self.qline.textChanged.connect(self.send_data)

        self.btn = QPushButton()
        # self.btn.clicked.connect(self.send_data)# send data

        layout.addWidget(self.label)
        layout.addWidget(self.qline)
        layout.addWidget(self.btn)
        self.setLayout(layout)

    def send_data(self, str_data):
        # str_data = self.qline.text()
        print(str_data)

        self._signal.emit(str_data)


class MainWindow(QMainWindow):
    def __init__(self):
        super().__init__()
        self.w = AnotherWindow()
        self.button = QPushButton("Push for Window")
        self.button.clicked.connect(self.show_new_window)
        # self.button.clicked.connect(self.toggle_window)

        self.input = QLineEdit()
        self.input.textChanged.connect(self.w.label.setText)

        self.qlabel = QLabel('测试窗口通信')

        layout = QVBoxLayout()
        layout.addWidget(self.button)
        layout.addWidget(self.input)
        layout.addWidget(self.qlabel)

        container = QWidget()
        container.setLayout(layout)
        self.setCentralWidget(container)

    def show_new_window(self, checked):
        self.w.show()
        self.w._signal.connect(self.process_data)

    def process_data(self, str_data):
        self.qlabel.setText(str_data)# change qlabel text

    def toggle_window(self, checked):
        if self.w.isVisible():
            self.w.hide()
        else:
            self.w.show()

app = QApplication(sys.argv)
w = MainWindow()
w.show()
app.exec_()