from PyQt5.QtCore import QObject, pyqtSignal

# 信号对象
class QSignal(QObject):
  # 定义信号
  # 在类创建时定义，不能在类创建后作为类的属性而添加
  # 指定信号传递参数的数量，类型等
  send_msg = pyqtSignal(str, str)

  def __init__(self):
    super(QSignal, self).__init__()

  def run(self):
    # 信号发射
    self.send_msg.emit('First arg', 'Second arg')

# 槽对象
class QSlot(QObject):
  def __init__(self):
    super(QSlot, self).__init__()

  def get(self, *args):
    # 信号接收
    print("Get message =>" + args[0], args[1], sep=', ')

if __name__ == '__main__':
  send = QSignal()
  slot = QSlot()

  # 将信号与槽函数绑定
  send.send_msg.connect(slot.get)
  # 外部调用 发射信号
  send.run()
  # 信号与槽解除关联
  send.send_msg.disconnect(slot.get)
  send.run()

import sys
from functools import partial
from PyQt5.QtCore import pyqtSignal
from PyQt5.QtWidgets import (QMainWindow, QApplication, QPushButton, QWidget, 
               QHBoxLayout)


class MainWindow(QMainWindow):
  btn_signal = pyqtSignal()
  def __init__(self):
    super(MainWindow, self).__init__()

    a = QPushButton("退出")
    # 给绑定的槽函数增加额外信息
    a.clicked.connect(partial(self.btn_clicked, 1))
    self.btn_signal.connect(self.close)

    self.setWindowTitle("演示")

    main_widget = QWidget()
    layout = QHBoxLayout()
    layout.addWidget(a)
    main_widget.setLayout(layout)
    # QMainWindow 不能设置布局
    self.setCentralWidget(main_widget)

  def btn_clicked(self, n):
    print(n)
    self.btn_signal.emit()

  def close(self):
    app = QApplication.instance()
    app.quit()


if __name__ == "__main__":
  # 在shell中执行
  app = QApplication(sys.argv)
  mywin = MainWindow()
  mywin.show()
  # 开始主循环，直到退出
  sys.exit(app.exec())

import sys
from PyQt5 import QtCore
from PyQt5.QtWidgets import (QWidget, QHBoxLayout, QPushButton, QMessageBox, 
               QLineEdit, QApplication)

# View
class MainWindow(QWidget):
  verifySignal = QtCore.pyqtSignal()

  def __init__(self, *args, **kwargs):
    super(MainWindow, self).__init__(*args, **kwargs)
    self.id_line = QLineEdit()
    self.id_line.setPlaceholderText("请输入账号")
    self.psd_line = QLineEdit()
    self.psd_line.setPlaceholderText("请输入密码")

    self.init()

  def init(self):

    layout = QHBoxLayout()
    self.setLayout(layout)

    self.button = QPushButton("登录")
    layout.addWidget(self.button)

    layout.addWidget(self.id_line)
    layout.addWidget(self.psd_line)
  
    # 连接定义的信号
    self.button.clicked.connect(self.verify_emit)

  def verify_emit(self):
    self.verifySignal.emit()

  def verify_ok(self):
    QMessageBox.about(self, "密码正确", "已经登录")

  def verify_no(self):
    QMessageBox.about(self, "你犯了一个粗误", "请重新检查输入")

# model
class Student(object):

  def __init__(self):
    self.name = "aaa"
    self.password = "aaa"

# control
class LoginControll(object):

  def __init__(self):
    # 不需要从命令行输入参数
    self._app = QApplication([])
    self._model = Student()
    self._view = MainWindow()
    self.init()

  def init(self):
    self._view.verifySignal.connect(self.verify_user)

  def verify_user(self):
    id_ = self._view.id_line.text()
    psd_ = self._view.psd_line.text()

    if id_ == self._model.name and psd_ == self._model.password:
      self._view.verify_ok()
    else:
      self._view.verify_no()

  def run(self):
    self._view.show()
    # 事件循环，直到应用退出
    return self._app.exec_()

# main.py
if __name__ == "__main__":
  login_control_ = LoginControll()
  # 退出主程序
  sys.exit(login_control_.run())

MVC-demo
├─ main.py
├─ UI
│  ├─ leftbtn_ui.py
│  ├─ login_ui.py
│  ├─ main_window_ui.py
│  └─ verify_ui.py
├─ control
│  ├─ controller.py
│  ├─ leftbtn_control.py
│  ├─ login_control.py
│  └─ verify_control.py
└─ model
    └─ model.py

class Controll(object):

  def __init__(self):

    self._app = QApplication([])

    self._stu = Student()

    self._view = MainWindow()
    self.init()

  def init(self):
    # 子 controller 作为局部变量，调用完后立刻消失，所以无法连接信号和槽
    # 这个问题困扰了我三天，可真是滑稽
    login_controller = login_control.Controller(self._view, self._stu.name, self._stu.password)