Question

我是python世界中GUI的初学者，我试图为sin（x），cos（x），tan（x）编写一个简单的函数求值程序。这是我的代码。

import matplotlib.pyplot as plt
import numpy as np
import sys
from PyQt4 import QtGui, QtCore


class Form(QtGui.QWidget) :
    def __init__(self):
        super(Form, self).__init__()

        layout = QtGui.QVBoxLayout(self)
        combo = QtGui.QComboBox()
        combo.addItem("Sin")
        combo.addItem("Cos")
        combo.addItem("Tan")

        parameter = QtGui.QLineEdit("np.linspace(lower,upper,dx)")
        parameter.selectAll()
        output = QtGui.QLineEdit("Output (Press Enter)")
        output.selectAll()

        layout.addWidget(combo)
        layout.addWidget(parameter)
        layout.addWidget(output)

        self.setLayout(layout)
        combo.setFocus()
        self.connect(output, QtCore.SIGNAL("returnPressed()"), self.updateUI) 
        self.setWindowTitle("Function Evaluator")

    def updateUI(self) :
        x = float(self.parameter_edit.text())
        f = str(eval(str(self.function_edit.text())))
        self.output_edit.setText(f)


app = QtGui.QApplication(sys.argv)
form = Form()
form.show()
app.exec_()

我该怎么做呢？我有一个特定功能的下拉列表，但我不知道如何为特定的下拉功能评估功能。或者我如何用x输入实际评估函数本身，并在我的updateUI方法中输出它。

Answer 1

QComboBox's项可以有一个名称和内容：

qCombo.addItem('Sin', 'np.sin')

以下是获取所选项目内容的方法：

content = qCombo.itemData(qCombo.currentIndex())

请注意，在python2中，已归还的内容包含在QVariant中;我们必须手动打开它：

content = content.toString()

因此，您的代码可能如下所示：

import matplotlib.pyplot as plt
import numpy as np
import sys
from PyQt4 import QtGui, QtCore


class Form(QtGui.QWidget):
    def __init__(self):
        super(Form, self).__init__()

        self.func_selector = QtGui.QComboBox()
        self.func_selector.setFocus()
        self.func_selector.addItem("Sin", 'np.sin')
        self.func_selector.addItem("Cos", 'np.cos')
        self.func_selector.addItem("Tan", 'np.tan')

        self.parameter_edit = QtGui.QLineEdit("np.linspace(lower, upper, n)")

        self.output_edit = QtGui.QLineEdit("Output (Press Enter)")
        self.output_edit.returnPressed.connect(self.updateUI)

        layout = QtGui.QVBoxLayout(self)
        layout.addWidget(self.func_selector)
        layout.addWidget(self.parameter_edit)
        layout.addWidget(self.output_edit)

        self.setLayout(layout)
        self.setWindowTitle("Function Evaluator")

    def updateUI(self):
        # A dictionary of local variables that can be used by eval()
        locs = {'lower': 0, 'upper': 2*np.pi, 'n': 10}

        x = self.parameter_edit.text()

        # Get a content of the selected QComboBox's item
        f = self.func_selector.itemData(self.func_selector.currentIndex())
        # In python2 a QComboBox item's content is wrapped in QVariant, so we must unwrap it:
        if sys.version_info.major == 2:
            f = f.toString()

        y = eval('{}({})'.format(f, x), None, locs)
        self.output_edit.setText(str(y))

        # if the function returns multiple values, show a plot
        if isinstance(y, np.ndarray):
            x_eval = eval(str(x), None, locs)
            plt.plot(x_eval, y)
            plt.show()


if __name__ == '__main__':
    app = QtGui.QApplication(sys.argv)
    form = Form()
    form.show()
    app.exec_()

简单的PyQt函数求值程序

1 个答案: