在Python中使用 PyQt5 的 1/4 英里计算器

先决条件： pyqt-5简介

在本文中，我们将了解如何使用PyQt5创建四分之一 (1/4) 英里计算器。四分之一英里计算器用于根据车辆的重量和功率确定车辆的终端速度（陷阱速度）和四分之一英里经过时间 (ET)。

下图显示了 1/4 英里计算器的外观：

1/4 英里计算器

四分之一英里计算器采用三个不同的经验方程来确定四分之一英里经过时间 (ET)。这些如下：

1. 罗杰亨廷顿方程：

Time = 6.290 × (Weight / Power)^(1/3)

2. 杰弗里福克斯方程：

Time = 6.269 × (Weight / Power)^(1/3)

3. Patrick Hale 方程：

Time = 5.825 × (Weight / Power)^(1/3)

注意：此处重量以磅 (lb) 为单位，功率以马力 (hp) 为单位。

GUI Implementation Steps : 
1. Create a heading label that display the calculator name 
2. Create label and combo box pair for selecting equation, label to show what user has to select and combo box to select 
3. Similarly create a pair of label and line edit to get the weight and power of car 
4. Create a push button to calculate the time 
5. Create a label to show the calculated time

Back-End Implementation : 
1. Make the combo box non editable 
2. Make the line edit to accept only the number as input 
3. Add action to the push button 
4. Inside the push button action get the text of the line edits 
5. Check if the line edit text is empty or zero then return so that function will not execute further 
6. Convert the text value into integer 
7. Get the selected option from the combo box and set constant value according to it 
8. Calculate the time and show this value through the label 
 

下面是实现：

Python3

# importing required libraries
from PyQt5.QtWidgets import *
from PyQt5 import QtCore, QtGui
from PyQt5.QtGui import *
from PyQt5.QtCore import *
  
import sys
  
  
class Window(QMainWindow):
  
    def __init__(self):
        super().__init__()
  
        # setting title
        self.setWindowTitle("Python ")
  
        # width of window
        self.w_width = 400
  
        # height of window
        self.w_height = 450
  
        # setting geometry
        self.setGeometry(100, 100, 
                         self.w_width, 
                         self.w_height)
  
        # calling method
        self.UiComponents()
  
        # showing all the widgets
        self.show()
  
    # method for components
    def UiComponents(self):
  
        # creating head label
        head = QLabel("1/4 Mile Calculator", 
                      self)
  
        # setting geometry to the head
        head.setGeometry(0, 10, 400, 60)
  
        # setting font
        font = QFont('Times', 15)
        font.setBold(True)
        font.setItalic(True)
        font.setUnderline(True)
  
        # setting font to the head
        head.setFont(font)
  
        # setting alignment of the head
        head.setAlignment(Qt.AlignCenter)
  
        # setting color effect to the head
        color = QGraphicsColorizeEffect(self)
        color.setColor(Qt.darkCyan)
        head.setGraphicsEffect(color)
  
        # creating a label
        e_label = QLabel("Equation", self)
  
        # setting properties  label
        e_label.setAlignment(Qt.AlignCenter)
        e_label.setGeometry(20, 100, 170, 40)
        e_label.setStyleSheet("QLabel"
                              "{"
                              "border : 2px solid black;"
                              "background : rgba(70, 70, 70, 35);"
                              "}")
        e_label.setFont(QFont('Times', 9))
  
        # creating a combo box to selected equation
        self.equation = QComboBox(self)
  
        # adding items to the combo box
        items = ["Huntington", "Fox", "Hale"]
        self.equation.addItems(items)
  
        # setting properties to the combo box
        self.equation.setFont(QFont('Times', 9))
        self.equation.setGeometry(200, 100, 180, 40)
        self.equation.setEditable(False)
  
  
        # creating a label
        w_label = QLabel("Car Weight (lb)", self)
  
        # setting properties to the label
        w_label.setAlignment(Qt.AlignCenter)
        w_label.setGeometry(20, 150, 170, 40)
        w_label.setStyleSheet("QLabel"
                              "{"
                              "border : 2px solid black;"
                              "background : rgba(70, 70, 70, 35);"
                              "}")
        w_label.setFont(QFont('Times', 9))
  
        # creating a QLineEdit object
        self.weight = QLineEdit(self)
  
        # accepting only number as input
        onlyInt = QIntValidator()
        self.weight.setValidator(onlyInt)
  
        # setting properties to the line edit
        self.weight.setGeometry(200, 150, 180, 40)
        self.weight.setAlignment(Qt.AlignCenter)
        self.weight.setFont(QFont('Times', 9))
  
        # creating a label
        p_label = QLabel("Engine Power (hp) ", self)
  
        # setting properties to the years label
        p_label.setAlignment(Qt.AlignCenter)
        p_label.setGeometry(20, 200, 170, 40)
        p_label.setStyleSheet("QLabel"
                              "{"
                              "border : 2px solid black;"
                              "background : rgba(70, 70, 70, 35);"
                              "}")
        p_label.setFont(QFont('Times', 9))
  
        # creating a QLineEdit object
        self.power = QLineEdit(self)
  
        # accepting only number as input
        onlyInt = QIntValidator()
        self.power.setValidator(onlyInt)
  
        # setting properties to the line edit
        self.power.setGeometry(200, 200, 180, 40)
        self.power.setAlignment(Qt.AlignCenter)
        self.power.setFont(QFont('Times', 9))
  
  
        # creating a push button
        calculate = QPushButton("Calculate Time", self)
  
        # setting geometry to the push button
        calculate.setGeometry(125, 270, 150, 40)
  
        # adding action to the calculate button
        calculate.clicked.connect(self.calculate_action)
  
        # creating a label to show percentile
        self.result = QLabel(self)
  
        # setting properties to result label
        self.result.setAlignment(Qt.AlignCenter)
        self.result.setGeometry(30, 340, 340, 80)
        self.result.setWordWrap(True)
        self.result.setStyleSheet("QLabel"
                                  "{"
                                  "border : 3px solid black;"
                                  "background : white;"
                                  "}")
        self.result.setFont(QFont('Arial', 11))
  
    # method for calculating the 
    # quarter-mile elapsed time (ET)
    def calculate_action(self):
  
  
        # getting weight of car
        weight = self.weight.text()
  
        # getting power of engine
        power = self.power.text()
  
        # if no input is given close the function
        if len(weight) == 0 or len(power) == 0:
            return
  
        # converting weight into integer
        weight = int(weight)
  
        # converting power into integer
        power = int(power)
  
        # if user enter total value as 0
        # return the function
        if power == 0 or weight == 0:
            return
  
        # getting the selected equation index
        equation = self.equation.currentIndex()
  
        # setting constant value according to the equation
        # Roger Huntington's constant
        if equation == 0:
            constant = 6.290
  
        # Geoffrey Fox's constant
        elif equation == 1:
            constant = 6.269
  
        # Patrick Hale's constant
        else:
            constant = 5.825
  
        # calculating the time
        result = constant * ((weight/power)**(1/3))
  
        # formatting the time
        result = "{:.2f}".format(result)
  
        # setting text to the result label
        self.result.setText("1/4 Mile Elapsed Time : "
                            + str(result) + " seconds")
  
  
# create pyqt5 app
App = QApplication(sys.argv)
  
# create the instance of our Window
window = Window()
  
# start the app
sys.exit(App.exec())

输出 ：