python - 退出/退出 PyQt 程序的正确方法

Question

我有一个带有登录屏幕的脚本，如果按下取消按钮，我想完全退出该应用程序。我尝试了 3 种方法:

1. 系统退出()
2. QApplication.quit()
3. QCoreApplication.instance().quit()

只有数字 1 有效。另外两个使对话框变白，然后闪烁然后挂起，我什至无法切换到其他应用程序。我的代码如下:

from PyQt5.QtCore import *
from PyQt5.QtGui import *
from PyQt5.QtSql import *
from PyQt5.QtWidgets import *


import csv
import sys
from datetime import datetime, timedelta, time
import os

from ci_co_table import *
from login import *

class Ci_Co(QMainWindow):
    """Check in and check out module"""

    def __init__(self, parent=None):
        QWidget.__init__(self, parent)
        self.ui = Ui_MainWindow()
        self.ui.setupUi(self)

class Login(QDialog):
    """User login """
    def __init__(self):
        QDialog.__init__(self)
        self.ui = Ui_login_form()
        self.ui.setupUi(self)
        self.ui.buttonBox.accepted.connect(lambda: self.handle_login(servers=servers))
        servers = {}
        with open('servers.csv', newline='') as csvfile:
            server_reader = csv.reader(csvfile)
            for row in server_reader:
                self.ui.cbo_db_name.addItem(row[1])
                servers[row[1]] = (row[0],row[2])

    def handle_login(self, servers=''):
        global user
        global pword
        global database
        global server
        global bg_colour
        user = self.ui.username.text()
        pword = self.ui.password.text()
        database = self.ui.cbo_db_name.currentText()
        server = servers[database][0]
        bg_colour = servers[database][1]


if __name__=="__main__":
    app=QApplication(sys.argv)
    global hotdate
    global hotdate_string
    global folio_num
    global user
    global pword
    global dbase
    global server
    pword = ""
    global database
    global bg_colour
    #Login
    while True:
        if Login().exec_() == QDialog.Accepted:
            db = QSqlDatabase.addDatabase("QPSQL");
            db.setHostName(server)
            db.setDatabaseName(database);
            db.setUserName(user);
            db.setPassword(pword)
            if (db.open()==False):     
                QMessageBox.critical(None, "Database Error", db.lastError().text())
            else:
                break
        else:
            #QApplication.quit()
            QCoreApplication.instance().quit()            
            #sys.exit()


    myapp = Ci_Co()
    myapp.show()
    sys.exit(app.exec_())

Answer 1

调用QCoreApplication.quit()与调用QCoreApplication.exit(0)是一样的。引用自qt docs :

After this function has been called, the application leaves the main event loop and returns from the call to exec(). The exec() function returns returnCode. If the event loop is not running, this function does nothing. [emphasis added]

所以 quit() 或 exit() 与 sys.exit() 完全不同。后者将终止程序，但前者只会终止事件循环(如果它正在运行)。

当用户取消登录对话框时，您的示例应该只调用 sys.exit() 来终止程序。否则，您的程序将陷入阻塞的 while 循环。