第三种方法找不到app.exec_()"这一行

如果你是在使用 Pyqt5 或 PySide2 开发 GUI 应用程序时，可能会使用如下方式来启动应用程序：

import sys
from PyQt5.QtWidgets import QApplication, QWidget

if __name__ == '__main__':
    app = QApplication(sys.argv)
    w = QWidget()
    w.show()
    sys.exit(app.exec_())

其中，`app.exec_()` 是启动 Pyqt5 或 PySide2 应用程序的方法。如果你的代码中没有这一行，可能是因为你使用了其他的 GUI 库或者启动方式，可以检查一下你的代码。如果你仍然无法解决问题，请提供更多的代码和错误信息，让我们看看问题所在。

相关问题

import sys from PyQt5.QtWidgets import QApplication, QWidget , QMainWindow from Calui1 import Ui_Form class Mywindow(QWidget,Ui_Form): def init(self): super(Mywindow,self).init() self.setupUi(self) def btnClear_clicked(self): self.lineEdit.clear() def btn1(self): self.lineEdit.insert("1") def btn2(self): self.lineEdit.insert("2") def btn3(self): self.lineEdit.insert("3") def btn4(self): self.lineEdit.insert("4") def btn5(self): self.lineEdit.insert("5") def btn6(self): self.lineEdit.insert("6") def btn7(self): self.lineEdit.insert("7") def btn8(self): self.lineEdit.insert("8") def btn9(self): self.lineEdit.insert("9") def btn0(self): self.lineEdit.insert("0") def btn_plus(self): self.lineEdit.insert("+") def btn_sub(self): self.lineEdit.insert("-") def btn_mul(self): self.lineEdit.insert("*") def btn_div(self): self.lineEdit.insert("/") def btnequal(self): text=self.lineEdit.text() self.lineEdit.insert("= %.2f" %(eval(text))) if name=='main': app=QApplication(sys.argv) win=Mywindow() win.pushButton_7.clicked.connect(win.btnClear_clicked()) win.pushButton.clicked.connect(win.btn1()) win.pushButton_2.clicked.connect(win.btn2()) win.pushButton_3.clicked.connect(win.btn3()) win.pushButton_4.clicked.connect(win.btn_plus()) win.pushButton_5.clicked.connect(win.btn4()) win.pushButton_6.clicked.connect(win.btn7()) win.pushButton_8.clicked.connect(win.btn5()) win.pushButton_9.clicked.connect(win.btn8()) win.pushButton_10.clicked.connect(win.btn0()) win.pushButton_11.clicked.connect(win.btn6()) win.pushButton_12.clicked.connect(win.btn9()) win.pushButton_13.clicked.connect(win.btnequal()) win.pushButton_14.clicked.connect(win.btn_sub()) win.pushButton_15.clicked.connect(win.btn_mul()) win.pushButton_16.clicked.connect(win.btn_div()) win.show() sys.exit(app.exec_())为什么会报错

这段代码有几个问题：

1. 在第一行导入语句中，`from PyQt5.QtWidgets import QApplication, QWidget , QMainWindow` 中间缺少逗号，应该为 `from PyQt5.QtWidgets import QApplication, QWidget, QMainWindow`。

2. 在 `Mywindow` 类的构造函数中，`init` 方法应该为 `__init__`。

3. 在 `Mywindow` 类中，所有的按钮槽函数应该以 `on_` 开头，例如 `on_btnClear_clicked`。

4. 在 `btnequal` 方法中，如果用户输入了非法表达式，可能会引发 `ZeroDivisionError` 异常，建议添加异常处理代码。

修改后的代码如下：

import sys
from PyQt5.QtWidgets import QApplication, QWidget, QMainWindow
from Calui1 import Ui_Form

class Mywindow(QWidget,Ui_Form):
    def __init__(self):
        super(Mywindow,self).__init__()
        self.setupUi(self)

    def on_btnClear_clicked(self):
        self.lineEdit.clear()

    def on_btn1_clicked(self):
        self.lineEdit.insert("1")

    def on_btn2_clicked(self):
        self.lineEdit.insert("2")

    def on_btn3_clicked(self):
        self.lineEdit.insert("3")

    def on_btn4_clicked(self):
        self.lineEdit.insert("4")

    def on_btn5_clicked(self):
        self.lineEdit.insert("5")

    def on_btn6_clicked(self):
        self.lineEdit.insert("6")

    def on_btn7_clicked(self):
        self.lineEdit.insert("7")

    def on_btn8_clicked(self):
        self.lineEdit.insert("8")

    def on_btn9_clicked(self):
        self.lineEdit.insert("9")

    def on_btn0_clicked(self):
        self.lineEdit.insert("0")

    def on_btn_plus_clicked(self):
        self.lineEdit.insert("+")

    def on_btn_sub_clicked(self):
        self.lineEdit.insert("-")

    def on_btn_mul_clicked(self):
        self.lineEdit.insert("*")

    def on_btn_div_clicked(self):
        self.lineEdit.insert("/")

    def on_btnequal_clicked(self):
        try:
            text = self.lineEdit.text()
            result = eval(text)
            self.lineEdit.setText("= %.2f" % result)
        except ZeroDivisionError:
            self.lineEdit.setText("除数不能为零")
        except Exception as e:
            self.lineEdit.setText(str(e))

if __name__=='__main__':
    app = QApplication(sys.argv)
    win = Mywindow()
    win.pushButton_7.clicked.connect(win.on_btnClear_clicked)
    win.pushButton.clicked.connect(win.on_btn1_clicked)
    win.pushButton_2.clicked.connect(win.on_btn2_clicked)
    win.pushButton_3.clicked.connect(win.on_btn3_clicked)
    win.pushButton_4.clicked.connect(win.on_btn_plus_clicked)
    win.pushButton_5.clicked.connect(win.on_btn4_clicked)
    win.pushButton_6.clicked.connect(win.on_btn7_clicked)
    win.pushButton_8.clicked.connect(win.on_btn5_clicked)
    win.pushButton_9.clicked.connect(win.on_btn8_clicked)
    win.pushButton_10.clicked.connect(win.on_btn0_clicked)
    win.pushButton_11.clicked.connect(win.on_btn6_clicked)
    win.pushButton_12.clicked.connect(win.on_btn9_clicked)
    win.pushButton_13.clicked.connect(win.on_btnequal_clicked)
    win.pushButton_14.clicked.connect(win.on_btn_sub_clicked)
    win.pushButton_15.clicked.connect(win.on_btn_mul_clicked)
    win.pushButton_16.clicked.connect(win.on_btn_div_clicked)
    win.show()
    sys.exit(app.exec_())

希望能帮到你！

import random import sys from PyQt5.QtCore import * from PyQt5.QtGui import * from PyQt5.QtWidgets import * from PyQt5.QtChart import * class RandomGenerator(QObject): dataReady = pyqtSignal(int) stopSignal = pyqtSignal() def init(self): super().init() self.queue = [] self.count = 0 def start(self): while True: val = random.randint(1, 49) if val < 50: self.queue.append(val) print(self.queue) if len(self.queue) == 1: self.dataReady.emit(val) else: self.count += 1 if self.count >= 2: self.stopSignal.emit() break class ChartDrawer(QObject): finished = pyqtSignal() def init(self, queue): super().init() self.queue = queue self.series = QLineSeries() def start(self): while True: if len(self.queue) > 0: print("start draw") val = self.queue.pop(0) self.series.append(self.series.count(), val) else: break self.finished.emit() print('end draw') class MainWindow(QMainWindow): def init(self): super().init() self.generator = RandomGenerator() self.drawer = ChartDrawer(self.generator.queue) self.chartView = QChartView() self.chart = QChart() self.chart.addSeries(self.drawer.series) self.chart.createDefaultAxes() self.chartView.setChart(self.chart) self.startButton = QPushButton("Start") self.startButton.clicked.connect(self.start) self.stopButton = QPushButton("Stop") self.stopButton.clicked.connect(self.stop) self.stopButton.setEnabled(False) self.statusBar().showMessage("Ready") layout = QVBoxLayout() layout.addWidget(self.chartView) layout.addWidget(self.startButton) layout.addWidget(self.stopButton) widget = QWidget() widget.setLayout(layout) self.setCentralWidget(widget) def start(self): self.statusBar().showMessage("Running") self.generatorThread = QThread() self.generator.moveToThread(self.generatorThread) self.generatorThread.started.connect(self.generator.start) self.generator.dataReady.connect(self.handleDataReady) self.generator.stopSignal.connect(self.handleStopSignal) self.generatorThread.start() self.drawerThread = QThread() self.drawer.moveToThread(self.drawerThread) self.drawer.finished.connect(self.handleDrawerFinished) self.drawerThread.start() self.startButton.setEnabled(False) self.stopButton.setEnabled(True) def stop(self): self.statusBar().showMessage("Stopping") self.generator.stopSignal.emit() self.generatorThread.quit() self.drawerThread.quit() self.startButton.setEnabled(True) self.stopButton.setEnabled(False) def handleDataReady(self, val): self.drawer.series.append(self.drawer.series.count(), val) def handleStopSignal(self): self.generatorThread.quit() def handleDrawerFinished(self): self.chartView.show() self.statusBar().showMessage("Finished") self.startButton.setEnabled(True) self.stopButton.setEnabled(False) if name == 'main': app = QApplication(sys.argv) window = MainWindow() window.show() sys.exit(app.exec_()) 检查上述代码为何在点击start按钮后只生成三个随机数后就停止生成数据，且未画图

在上述代码中，当随机数生成的值大于等于50时，没有将这个值加入到队列中。因此，队列中的随机数数量不足以绘制图表。解决方法是将第11行代码修改为`if val <= 50:`。另外，在 `RandomGenerator` 类的 `start` 方法中，当队列中只有一个随机数时，应该使用 `self.queue[0]` 而不是 `val`。这些修改后，点击 start 按钮后，会绘制出完整的图表。