Ps：水平有限，欢迎建议和挑错
我们在此之前，学习了PyQt的主窗口（QMainwindow），按钮（Qpushbutton），标签栏（QLabel），文本框编辑框（LineEdit）4个组件。
我们可以尝试做一个由这些组件组成的小项目。同时有这4个组件的，常见的一种界面就是登录框。
网上有许多教程，是关于登录框的。
我们今天也做一个自己的登录框。

素材

首先我们这次登录框需要一些素材，平面设计素材，为了让我们的登录框看起来更好看。

Background.jpg logo.png

创建主窗口

创建一个主窗口，命名为login.py

from PyQt5 import QtCore, QtGui, QtWidgets

class Ui_MainWindow(object):
    def setupUi(self, MainWindow):
        MainWindow.setObjectName("MainWindow")
        MainWindow.resize(386, 127)
        self.centralWidget = QtWidgets.QWidget(MainWindow)
        self.centralWidget.setObjectName("centralWidget")
        MainWindow.setCentralWidget(self.centralWidget)

        self.retranslateUi(MainWindow)
        QtCore.QMetaObject.connectSlotsByName(MainWindow)

    def retranslateUi(self, MainWindow):
        _translate = QtCore.QCoreApplication.translate
        MainWindow.setWindowTitle(_translate("MainWindow", "MainWindow"))


if __name__ == "__main__":
    import sys
    app = QtWidgets.QApplication(sys.argv)
    MainWindow = QtWidgets.QMainWindow()
    ui = Ui_MainWindow()
    ui.setupUi(MainWindow)
    MainWindow.show()
    sys.exit(app.exec_())

主窗口

美化一下
添加logo图片与背景图

from PyQt5.QtGui import QIcon
        MainWindow.setWindowIcon(QIcon('logo.png'))
        MainWindow.setStyleSheet("background-image:url(Background.jpg)")

image.png

到这步的所有代码：

from PyQt5 import QtCore, QtGui, QtWidgets

class Ui_MainWindow(object):
    def setupUi(self, MainWindow):
        MainWindow.setObjectName("MainWindow")
        MainWindow.resize(386, 127)
        MainWindow.setWindowIcon(QIcon('logo.png'))
        MainWindow.setStyleSheet("background-image:url(Background.jpg)")
        self.centralWidget = QtWidgets.QWidget(MainWindow)
        self.centralWidget.setObjectName("centralWidget")
        MainWindow.setCentralWidget(self.centralWidget)

        self.retranslateUi(MainWindow)
        QtCore.QMetaObject.connectSlotsByName(MainWindow)

    def retranslateUi(self, MainWindow):
        _translate = QtCore.QCoreApplication.translate
        MainWindow.setWindowTitle(_translate("MainWindow", "一颗数据小白菜"))

if __name__ == "__main__":
    import sys
    app = QtWidgets.QApplication(sys.argv)
    MainWindow = QtWidgets.QMainWindow()
    ui = Ui_MainWindow()
    ui.setupUi(MainWindow)
    MainWindow.show()
    sys.exit(app.exec_())

添加组件

添加2个Qlabel，显示帐号、密码
添加2个LineEdit，提示输入和接收密码帐号
添加2个Qpushbutton，绑定事件触发

        self.lineEdit = QtWidgets.QLineEdit(self.centralWidget)
        self.lineEdit.setGeometry(QtCore.QRect(250, 20, 100, 20))
        self.lineEdit.setText("")
        self.lineEdit.setObjectName("lineEdit")
        self.lineEdit_2 = QtWidgets.QLineEdit(self.centralWidget)
        self.lineEdit_2.setGeometry(QtCore.QRect(250, 50, 100, 20))
        self.lineEdit_2.setText("")

        #密码输入框调整为密码模 https://www.jianshu.com/p/3915e033c87a 点击介绍密码模式
        self.lineEdit_2.setEchoMode(QtWidgets.QLineEdit.Password)

        self.lineEdit_2.setObjectName("lineEdit_2")
        self.label = QtWidgets.QLabel(self.centralWidget)
        self.label.setGeometry(QtCore.QRect(200, 24, 24, 12))
        self.label.setTextFormat(QtCore.Qt.AutoText)
        self.label.setObjectName("label")
        self.label_2 = QtWidgets.QLabel(self.centralWidget)
        self.label_2.setGeometry(QtCore.QRect(200, 54, 24, 12))
        self.label_2.setObjectName("label_2")
        self.pushButton = QtWidgets.QPushButton(self.centralWidget)
        self.pushButton.setGeometry(QtCore.QRect(190, 90, 75, 23))
        self.pushButton.setObjectName("pushButton")
        self.pushButton_2 = QtWidgets.QPushButton(self.centralWidget)
        self.pushButton_2.setGeometry(QtCore.QRect(290, 90, 75, 23))
        self.pushButton_2.setObjectName("pushButton_2")

        self.lineEdit.setPlaceholderText(_translate("MainWindow", "请输入帐号"))
        self.lineEdit_2.setPlaceholderText(_translate("MainWindow", "请输入密码"))
        self.label.setText(_translate("MainWindow", "帐号"))
        self.label_2.setText(_translate("MainWindow", "密码"))
        self.pushButton.setText(_translate("MainWindow", "确定"))
        self.pushButton_2.setText(_translate("MainWindow", "取消"))

image.png

组件大小位置，需要仔细调整，我这个是已经调整好的。
到这步的所有代码：

from PyQt5 import QtCore, QtGui, QtWidgets
from PyQt5.QtGui import QIcon

class Ui_MainWindow(object):
    def setupUi(self, MainWindow):
        MainWindow.setObjectName("MainWindow")
        MainWindow.resize(386, 127)
        MainWindow.setWindowIcon(QIcon('logo.png'))
        MainWindow.setStyleSheet("background-image:url(Background.jpg)")
        self.centralWidget = QtWidgets.QWidget(MainWindow)
        self.centralWidget.setObjectName("centralWidget")
        self.lineEdit = QtWidgets.QLineEdit(self.centralWidget)
        self.lineEdit.setGeometry(QtCore.QRect(250, 20, 100, 20))
        self.lineEdit.setText("")
        self.lineEdit.setObjectName("lineEdit")
        self.lineEdit_2 = QtWidgets.QLineEdit(self.centralWidget)
        self.lineEdit_2.setGeometry(QtCore.QRect(250, 50, 100, 20))
        self.lineEdit_2.setText("")
        self.lineEdit_2.setEchoMode(QtWidgets.QLineEdit.Password)
        self.lineEdit_2.setObjectName("lineEdit_2")
        self.label = QtWidgets.QLabel(self.centralWidget)
        self.label.setGeometry(QtCore.QRect(200, 24, 24, 12))
        self.label.setTextFormat(QtCore.Qt.AutoText)
        self.label.setObjectName("label")
        self.label_2 = QtWidgets.QLabel(self.centralWidget)
        self.label_2.setGeometry(QtCore.QRect(200, 54, 24, 12))
        self.label_2.setObjectName("label_2")
        self.pushButton = QtWidgets.QPushButton(self.centralWidget)
        self.pushButton.setGeometry(QtCore.QRect(190, 90, 75, 23))
        self.pushButton.setObjectName("pushButton")
        self.pushButton_2 = QtWidgets.QPushButton(self.centralWidget)
        self.pushButton_2.setGeometry(QtCore.QRect(290, 90, 75, 23))
        self.pushButton_2.setObjectName("pushButton_2")
        MainWindow.setCentralWidget(self.centralWidget)

        self.retranslateUi(MainWindow)
        QtCore.QMetaObject.connectSlotsByName(MainWindow)

    def retranslateUi(self, MainWindow):
        _translate = QtCore.QCoreApplication.translate
        MainWindow.setWindowTitle(_translate("MainWindow", "一颗数据小白菜"))
        self.lineEdit.setPlaceholderText(_translate("MainWindow", "请输入帐号"))
        self.lineEdit_2.setPlaceholderText(_translate("MainWindow", "请输入密码"))
        self.label.setText(_translate("MainWindow", "帐号"))
        self.label_2.setText(_translate("MainWindow", "密码"))
        self.pushButton.setText(_translate("MainWindow", "确定"))
        self.pushButton_2.setText(_translate("MainWindow", "取消"))


if __name__ == "__main__":
    import sys
    app = QtWidgets.QApplication(sys.argv)
    MainWindow = QtWidgets.QMainWindow()
    ui = Ui_MainWindow()
    ui.setupUi(MainWindow)
    MainWindow.show()
    sys.exit(app.exec_())

所有组件都已经完成，接下来就是定义事件了。

密码验证

我们假设帐号为admin。密码为123456
我们来定义一个逻辑函数，验证帐号密码

1.获取输入帐号密码

login_user = self.lineEdit.text()
login_password = self.lineEdit_2.text()

2.判断输入帐号密码

我们先准备新建一个主窗口，如果帐号密码是对的，就调用这个主窗口，显示这个主窗口，如果密码是错的，就弹出警告。
另一个主窗口代码如下，命名为hello.py，保存在login.py同一级目录

from PyQt5 import QtCore, QtGui, QtWidgets

class hello_mainWindow(object):
    def setupUi(self, mainWindow):
        mainWindow.setObjectName("mainWindow")
        mainWindow.setWindowModality(QtCore.Qt.WindowModal)
        mainWindow.resize(624, 511)
        self.retranslateUi(mainWindow)
        QtCore.QMetaObject.connectSlotsByName(mainWindow)
    def retranslateUi(self, mainWindow):
        _translate = QtCore.QCoreApplication.translate
        mainWindow.setWindowTitle(_translate("mainWindow", "hello word"))

if __name__ == "__main__":
    import sys
    app = QtWidgets.QApplication(sys.argv)
    mainWindow = QtWidgets.QMainWindow()
    ui = hello_mainWindow()
    ui.setupUi(mainWindow)
    mainWindow.show()
    sys.exit(app.exec_())

同时在login.py文件中import这个hello窗口

from hello import *

下面是判断逻辑，写在 login.py 文件中

    def word_get(self):
        login_user = self.lineEdit.text()
        login_password = self.lineEdit_2.text()
        print(login_user,login_password)

        if login_user == 'admin' and login_password == '123456':
            ui_hello.show()
            MainWindow.close()


        else:
            QMessageBox.warning(self,
                    "警告",
                    "用户名或密码错误！",
                    QMessageBox.Yes)
            self.lineEdit.setFocus()

这段代码运行时，会判断密码帐号是否正确，正确就会打开hello窗口，并且关闭登录框，如果不对，则会弹出警告框。

3.绑定确定按钮事件

self.pushButton.clicked.connect(self.word_get)

但是会出现：
‘Ui_MainWindow‘ object has no attribute ‘show‘的错误，这时候我们要对代码进行修改。

====login.py====

class Ui_MainWindow(QtWidgets.QMainWindow):
    def __init__(self):
        super(Ui_MainWindow,self).__init__()
        self.setupUi(self)
        self.retranslateUi(self)

====hello.py====

class hello_mainWindow(QtWidgets.QMainWindow):
    def __init__(self):
        super(hello_mainWindow,self).__init__()
        self.setupUi(self)

这时候：
login.py整个代码为：

from PyQt5 import QtCore, QtGui, QtWidgets, Qt
from PyQt5.QtGui import QIcon
from hello import *
from PyQt5.QtWidgets import *
from PyQt5.QtCore import *

class Ui_MainWindow(QtWidgets.QMainWindow):

    def __init__(self):
        super(Ui_MainWindow,self).__init__()
        self.setupUi(self)
        self.retranslateUi(self)

    def setupUi(self, MainWindow):
        MainWindow.setObjectName("MainWindow")
        MainWindow.resize(386, 127)
        MainWindow.setWindowIcon(QIcon('logo.png'))
        MainWindow.setStyleSheet("background-image:url(Background.jpg)")
        self.centralWidget = QtWidgets.QWidget(MainWindow)
        self.centralWidget.setObjectName("centralWidget")
        self.lineEdit = QtWidgets.QLineEdit(self.centralWidget)
        self.lineEdit.setGeometry(QtCore.QRect(250, 20, 100, 20))
        self.lineEdit.setText("")
        self.lineEdit.setObjectName("lineEdit")
        self.lineEdit_2 = QtWidgets.QLineEdit(self.centralWidget)
        self.lineEdit_2.setGeometry(QtCore.QRect(250, 50, 100, 20))
        self.lineEdit_2.setText("")
        self.lineEdit_2.setEchoMode(QtWidgets.QLineEdit.Password)
        self.lineEdit_2.setObjectName("lineEdit_2")
        self.label = QtWidgets.QLabel(self.centralWidget)
        self.label.setGeometry(QtCore.QRect(200, 24, 24, 12))
        self.label.setTextFormat(QtCore.Qt.AutoText)
        self.label.setObjectName("label")
        self.label_2 = QtWidgets.QLabel(self.centralWidget)
        self.label_2.setGeometry(QtCore.QRect(200, 54, 24, 12))
        self.label_2.setObjectName("label_2")
        self.pushButton = QtWidgets.QPushButton(self.centralWidget)
        self.pushButton.setGeometry(QtCore.QRect(190, 90, 75, 23))
        self.pushButton.setObjectName("pushButton")
        self.pushButton_2 = QtWidgets.QPushButton(self.centralWidget)
        self.pushButton_2.setGeometry(QtCore.QRect(290, 90, 75, 23))
        self.pushButton_2.setObjectName("pushButton_2")
        MainWindow.setCentralWidget(self.centralWidget)

        self.pushButton.clicked.connect(self.word_get)

        self.retranslateUi(MainWindow)
        QtCore.QMetaObject.connectSlotsByName(MainWindow)

    def retranslateUi(self, MainWindow):
        _translate = QtCore.QCoreApplication.translate
        MainWindow.setWindowTitle(_translate("MainWindow", "一颗数据小白菜"))
        self.lineEdit.setPlaceholderText(_translate("MainWindow", "请输入帐号"))
        self.lineEdit_2.setPlaceholderText(_translate("MainWindow", "请输入密码"))
        self.label.setText(_translate("MainWindow", "帐号"))
        self.label_2.setText(_translate("MainWindow", "密码"))
        self.pushButton.setText(_translate("MainWindow", "确定"))
        self.pushButton_2.setText(_translate("MainWindow", "取消"))

    def word_get(self):
        login_user = self.lineEdit.text()
        login_password = self.lineEdit_2.text()
        if login_user == 'admin' and login_password == '123456':
            ui_hello.show()
            MainWindow.close()
        else:
            QMessageBox.warning(self,
                    "警告",
                    "用户名或密码错误！",
                    QMessageBox.Yes)
            self.lineEdit.setFocus()
if __name__ == "__main__":
    import sys
    app = QtWidgets.QApplication(sys.argv)
    MainWindow = QtWidgets.QMainWindow()
    ui = Ui_MainWindow()
    ui_hello = hello_mainWindow()
    ui.setupUi(MainWindow)
    MainWindow.show()
    sys.exit(app.exec_())

hello.py文件整个代码为：

from PyQt5 import QtCore, QtGui, QtWidgets

class hello_mainWindow(QtWidgets.QMainWindow):

    def __init__(self):
        super(hello_mainWindow,self).__init__()
        self.setupUi(self)
        self.retranslateUi(self)

    def setupUi(self, mainWindow):
        mainWindow.setObjectName("mainWindow")
        mainWindow.setWindowModality(QtCore.Qt.WindowModal)
        mainWindow.resize(624, 511)
        self.retranslateUi(mainWindow)
        QtCore.QMetaObject.connectSlotsByName(mainWindow)
    def retranslateUi(self, mainWindow):
        _translate = QtCore.QCoreApplication.translate
        mainWindow.setWindowTitle(_translate("mainWindow", "hello word"))

if __name__ == "__main__":
    import sys
    app = QtWidgets.QApplication(sys.argv)
    mainWindow = QtWidgets.QMainWindow()
    ui = hello_mainWindow()
    ui.setupUi(mainWindow)
    mainWindow.show()
    sys.exit(app.exec_())

4.绑定取消按钮事件

self.pushButton_2.clicked.connect(MainWindow.close)

点击取消，退出登录框

总结

最终代码为：

====login.py

from PyQt5 import QtCore, QtGui, QtWidgets, Qt
from PyQt5.QtGui import QIcon
from hello import *
from PyQt5.QtWidgets import *
from PyQt5.QtCore import *

class Ui_MainWindow(QtWidgets.QMainWindow):

    def __init__(self):
        super(Ui_MainWindow,self).__init__()
        self.setupUi(self)
        self.retranslateUi(self)

    def setupUi(self, MainWindow):
        MainWindow.setObjectName("MainWindow")
        MainWindow.resize(386, 127)
        MainWindow.setWindowIcon(QIcon('logo.png'))
        MainWindow.setStyleSheet("background-image:url(Background.jpg)")
        self.centralWidget = QtWidgets.QWidget(MainWindow)
        self.centralWidget.setObjectName("centralWidget")
        self.lineEdit = QtWidgets.QLineEdit(self.centralWidget)
        self.lineEdit.setGeometry(QtCore.QRect(250, 20, 100, 20))
        self.lineEdit.setText("")
        self.lineEdit.setObjectName("lineEdit")
        self.lineEdit_2 = QtWidgets.QLineEdit(self.centralWidget)
        self.lineEdit_2.setGeometry(QtCore.QRect(250, 50, 100, 20))
        self.lineEdit_2.setText("")
        self.lineEdit_2.setEchoMode(QtWidgets.QLineEdit.Password)
        self.lineEdit_2.setObjectName("lineEdit_2")
        self.label = QtWidgets.QLabel(self.centralWidget)
        self.label.setGeometry(QtCore.QRect(200, 24, 24, 12))
        self.label.setTextFormat(QtCore.Qt.AutoText)
        self.label.setObjectName("label")
        self.label_2 = QtWidgets.QLabel(self.centralWidget)
        self.label_2.setGeometry(QtCore.QRect(200, 54, 24, 12))
        self.label_2.setObjectName("label_2")
        self.pushButton = QtWidgets.QPushButton(self.centralWidget)
        self.pushButton.setGeometry(QtCore.QRect(190, 90, 75, 23))
        self.pushButton.setObjectName("pushButton")
        self.pushButton_2 = QtWidgets.QPushButton(self.centralWidget)
        self.pushButton_2.setGeometry(QtCore.QRect(290, 90, 75, 23))
        self.pushButton_2.setObjectName("pushButton_2")
        MainWindow.setCentralWidget(self.centralWidget)

        self.pushButton.clicked.connect(self.word_get)
        self.pushButton_2.clicked.connect(MainWindow.close)

        self.retranslateUi(MainWindow)
        QtCore.QMetaObject.connectSlotsByName(MainWindow)

    def retranslateUi(self, MainWindow):
        _translate = QtCore.QCoreApplication.translate
        MainWindow.setWindowTitle(_translate("MainWindow", "一颗数据小白菜"))
        self.lineEdit.setPlaceholderText(_translate("MainWindow", "请输入帐号"))
        self.lineEdit_2.setPlaceholderText(_translate("MainWindow", "请输入密码"))
        self.label.setText(_translate("MainWindow", "帐号"))
        self.label_2.setText(_translate("MainWindow", "密码"))
        self.pushButton.setText(_translate("MainWindow", "确定"))
        self.pushButton_2.setText(_translate("MainWindow", "取消"))

    def word_get(self):
        login_user = self.lineEdit.text()
        login_password = self.lineEdit_2.text()
        if login_user == 'admin' and login_password == '123456':
            ui_hello.show()
            MainWindow.close()
        else:
            QMessageBox.warning(self,
                    "警告",
                    "用户名或密码错误！",
                    QMessageBox.Yes)
            self.lineEdit.setFocus()
if __name__ == "__main__":
    import sys
    app = QtWidgets.QApplication(sys.argv)
    MainWindow = QtWidgets.QMainWindow()
    ui = Ui_MainWindow()
    ui_hello = hello_mainWindow()
    ui.setupUi(MainWindow)
    MainWindow.show()
    sys.exit(app.exec_())

====hello.py

from PyQt5 import QtCore, QtGui, QtWidgets

class hello_mainWindow(QtWidgets.QMainWindow):

    def __init__(self):
        super(hello_mainWindow,self).__init__()
        self.setupUi(self)
        self.retranslateUi(self)

    def setupUi(self, mainWindow):
        mainWindow.setObjectName("mainWindow")
        mainWindow.setWindowModality(QtCore.Qt.WindowModal)
        mainWindow.resize(624, 511)
        self.retranslateUi(mainWindow)
        QtCore.QMetaObject.connectSlotsByName(mainWindow)
    def retranslateUi(self, mainWindow):
        _translate = QtCore.QCoreApplication.translate
        mainWindow.setWindowTitle(_translate("mainWindow", "hello word"))

if __name__ == "__main__":
    import sys
    app = QtWidgets.QApplication(sys.argv)
    mainWindow = QtWidgets.QMainWindow()
    ui = hello_mainWindow()
    ui.setupUi(mainWindow)
    mainWindow.show()
    sys.exit(app.exec_())

效果如下：

效果图.gif