数据库作业二-------gui实现简单计算器

因为上个学期使用过Qt(C++)写过一个简单的地图软件，所以这次我使用Qt来完成作业，由于最近在学python，所以就干脆用python + Qt来实现了，顺便练习一下python的语法，但是python我用的实在是太不熟练了，代码写的又臭又长，c++40行能写完的我python写了200行，安装pyqt5也花了不少时间,用python的原因主要是不会爆int，不用自己手写高精度了，碰到大数和大数的运算不用担心会超出范围，而且python内置的eval函数可以直接计算出表达式的值。。

1.pycharm上pyqt5和qtdesigner的安装

 

pycharm安装pyqt5的过程网上教程很多，不赘述了，但是配置参数网上很多教程都是错的，在pyuic的参数配置中,网上的参数大多是-m,但是-m会出现这个错误，这时候把参数改成

$FileName$ -o $FileNameWithoutExtension$.py

 

 即可。还有一个问题是在ui文件转py文件时出现error，这主要是右侧栏没有选中ui文件，选中后再转换就会生成py文件了。

 

 

2.简易计算器的实现

实际操作中，我发现由于存在各种输入的情况，比如连续输入两个加号，或者连续输入两个等于号或是除0，这种情况都会导致程序终止，所以我们使用一个变量flag来记录当前的符号数，当符号数为0时，符号只接受+，-，*，/，之后把符号数+1，当符号数为1时，只接受=号，此时符号数再加1，当符号数为2时，就进行完一组运算了，此时若接受到数字，就把符号数和文本框文字清空，重新计算,这样程序就不会被非法输入所干扰了。

使用qtdesigned实现的ui代码如下

import sys
from PyQt5 import QtCore, QtGui, QtWidgets
from PyQt5.QtWidgets import QApplication, QWidget
class Ui_MainWindow(object):
    flag = 0
    def setupUi(self, MainWindow):
        MainWindow.setObjectName("MainWindow")
        MainWindow.resize(705, 600)
        self.centralwidget = QtWidgets.QWidget(MainWindow)
        self.centralwidget.setObjectName("centralwidget")
        self.one = QtWidgets.QPushButton(self.centralwidget)
        self.one.setGeometry(QtCore.QRect(180, 160, 61, 51))
        self.one.setObjectName("one")
        self.label = QtWidgets.QLabel(self.centralwidget)
        self.label.setGeometry(QtCore.QRect(160, 70, 341, 61))
        self.label.setFrameShape(QtWidgets.QFrame.WinPanel)
        self.label.setText("")
        self.label.setTextFormat(QtCore.Qt.AutoText)
        self.label.setObjectName("label")
        self.add = QtWidgets.QPushButton(self.centralwidget)
        self.add.setGeometry(QtCore.QRect(430, 160, 31, 31))
        self.add.setObjectName("add")
        self.two = QtWidgets.QPushButton(self.centralwidget)
        self.two.setGeometry(QtCore.QRect(260, 160, 61, 51))
        self.two.setObjectName("two")
        self.three = QtWidgets.QPushButton(self.centralwidget)
        self.three.setGeometry(QtCore.QRect(340, 160, 61, 51))
        self.three.setObjectName("three")
        self.four = QtWidgets.QPushButton(self.centralwidget)
        self.four.setGeometry(QtCore.QRect(180, 220, 61, 51))
        self.four.setObjectName("four")
        self.five = QtWidgets.QPushButton(self.centralwidget)
        self.five.setGeometry(QtCore.QRect(260, 220, 61, 51))
        self.five.setObjectName("five")
        self.six = QtWidgets.QPushButton(self.centralwidget)
        self.six.setGeometry(QtCore.QRect(340, 220, 61, 51))
        self.six.setObjectName("six")
        self.seven = QtWidgets.QPushButton(self.centralwidget)
        self.seven.setGeometry(QtCore.QRect(180, 280, 61, 51))
        self.seven.setObjectName("seven")
        self.eight = QtWidgets.QPushButton(self.centralwidget)
        self.eight.setGeometry(QtCore.QRect(260, 280, 61, 51))
        self.eight.setObjectName("eight")
        self.nine = QtWidgets.QPushButton(self.centralwidget)
        self.nine.setGeometry(QtCore.QRect(340, 280, 61, 51))
        self.nine.setObjectName("nine")
        self.sub = QtWidgets.QPushButton(self.centralwidget)
        self.sub.setGeometry(QtCore.QRect(430, 210, 31, 31))
        self.sub.setObjectName("sub")
        self.mul = QtWidgets.QPushButton(self.centralwidget)
        self.mul.setGeometry(QtCore.QRect(430, 260, 31, 31))
        self.mul.setObjectName("mul")
        self.divide = QtWidgets.QPushButton(self.centralwidget)
        self.divide.setGeometry(QtCore.QRect(430, 310, 31, 31))
        self.divide.setObjectName("divide")
        self.sp = QtWidgets.QPushButton(self.centralwidget)
        self.sp.setGeometry(QtCore.QRect(480, 180, 31, 31))
        self.sp.setObjectName("sp")
        self.equal = QtWidgets.QPushButton(self.centralwidget)
        self.equal.setGeometry(QtCore.QRect(480, 280, 31, 31))
        self.equal.setObjectName("equal")
        self.zero = QtWidgets.QPushButton(self.centralwidget)
        self.zero.setGeometry(QtCore.QRect(260, 340, 61, 51))
        self.zero.setObjectName("zero")
        MainWindow.setCentralWidget(self.centralwidget)
        self.menubar = QtWidgets.QMenuBar(MainWindow)
        self.menubar.setGeometry(QtCore.QRect(0, 0, 705, 23))
        self.menubar.setObjectName("menubar")
        MainWindow.setMenuBar(self.menubar)
        self.statusbar = QtWidgets.QStatusBar(MainWindow)
        self.statusbar.setObjectName("statusbar")
        MainWindow.setStatusBar(self.statusbar)
        self.retranslateUi(MainWindow)
        QtCore.QMetaObject.connectSlotsByName(MainWindow)
    def retranslateUi(self, MainWindow):
        _translate = QtCore.QCoreApplication.translate
        MainWindow.setWindowTitle(_translate("MainWindow", "Calculator"))
        self.one.setText(_translate("MainWindow", "1"))
        self.one.clicked.connect(self.onee);
        self.add.setText(_translate("MainWindow", "+"))
        self.add.clicked.connect(self.adde);
        self.two.setText(_translate("MainWindow", "2"))
        self.two.clicked.connect(self.twoe);
        self.three.setText(_translate("MainWindow", "3"))
        self.three.clicked.connect(self.threee);
        self.four.setText(_translate("MainWindow", "4"))
        self.four.clicked.connect(self.foure);
        self.five.setText(_translate("MainWindow", "5"))
        self.five.clicked.connect(self.fivee);
        self.six.setText(_translate("MainWindow", "6"))
        self.six.clicked.connect(self.sixe);
        self.seven.setText(_translate("MainWindow", "7"))
        self.seven.clicked.connect(self.sevene);
        self.eight.setText(_translate("MainWindow", "8"))
        self.eight.clicked.connect(self.eighte);
        self.nine.setText(_translate("MainWindow", "9"))
        self.nine.clicked.connect(self.ninee);
        self.sub.setText(_translate("MainWindow", "-"))
        self.sub.clicked.connect(self.sube);
        self.mul.setText(_translate("MainWindow", "*"))
        self.mul.clicked.connect(self.mule);
        self.divide.setText(_translate("MainWindow", "/"))
        self.divide.clicked.connect(self.devidee);
        self.sp.setText(_translate("MainWindow", "CE"))
        self.sp.clicked.connect(self.spe);
        self.equal.setText(_translate("MainWindow", "="))
        self.equal.clicked.connect(self.equale);
        self.zero.setText(_translate("MainWindow", "0"))
        self.zero.clicked.connect(self.zeroe);

本来按照面向对象编程的原则，我要再写一个类继承ui的，但是我还没学会python的继承还有接口啥的，所以就再ui里继续写下去了，代码如下

    def onee(self):
        if self.flag == 2:
            self.label.clear()
            self.flag = 0
        self.label.setText(self.label.text() + "1")
    def twoe(self):
        if self.flag == 2:
            self.label.clear()
            self.flag = 0
        self.label.setText(self.label.text() + "2")
    def threee(self):
        if self.flag == 2:
            self.label.clear()
            self.flag = 0
        self.label.setText(self.label.text() + "3")
    def foure(self):
        if self.flag == 2:
            self.label.clear()
            self.flag = 0
        self.label.setText(self.label.text() + "4")
    def fivee(self):
        if self.flag == 2:
            self.label.clear()
            self.flag = 0
        self.label.setText(self.label.text() + "5")
    def sixe(self):
        if self.flag == 2:
            self.label.clear()
            self.flag = 0
        self.label.setText(self.label.text() + "6")
    def sevene(self):
        if self.flag == 2:
            self.label.clear()
            self.flag = 0
        self.label.setText(self.label.text() + "7")
    def eighte(self):
        if self.flag == 2:
            self.label.clear()
            self.flag = 0
        self.label.setText(self.label.text() + "8")
    def ninee(self):
        if self.flag == 2:
            self.label.clear()
            self.flag = 0
        self.label.setText(self.label.text() + "9")
    def zeroe(self):
        if self.flag == 2:
            self.label.clear()
            self.flag = 0
        self.label.setText(self.label.text() + "0")
    def spe(self):
        if self.flag :
            self.flag = 0
        self.label.clear()
    def devidee(self):
        if self.flag: return
        self.label.setText(self.label.text() + "/")
        self.flag+=1
    def equale(self):
        if self.flag !=1 : return
        try:
            s = self.label.text() + '=' + str(eval(self.label.text()))
        except:
            self.label.setText("Error")
            self.flag = 2
        else:
            self.label.setText(s)
            self.flag += 1
    def mule(self):
        if self.flag: return
        self.label.setText(self.label.text() + "*")
        self.flag += 1
    def adde(self):
        if self.flag: return
        self.label.setText(self.label.text() + "+")
        self.flag += 1
    def sube(self):
        if self.flag: return
        self.label.setText(self.label.text() + "-")
        self.flag += 1

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

最后附上成果：（这是碰到除0时或者输入的符号不对就输出error）