如果用户没有输入某个单词，则输出错误信息

Question

这是我之前问过的一个问题的副本，但有点不同。

我是一个编程初学者（从来没有编程过），我已经给了一个任务（学校）来制作一个程序，要求用户提供一个形状，然后根据给定的尺寸计算该形状的体积用户。但如果用户没有输入“quit”，程序应该不断询问用户形状并继续计算卷，并且当用户输入“quit”时，程序将假设打印出卷的列表计算。三个形状是立方体，金字塔和椭圆体。

，例如，如果在立方体，立方体，棱锥，棱锥形，椭圆体，然后在用户键入退出（与必要的尺寸沿着计算体积），则程序应该打印出：

立方体体积：4 ，5

金字塔卷：6,7

椭球体积：8

注：这些数字只是例如。

我已经成功（有点）让程序注意到错误，并让程序重复询问用户形状和计算体积，直到输入“quit”。但是，如果用户没有例如进入立方体，那么最终的输出应该是：

立方体体积：你有没有做过任何计算多维数据集

金字塔卷：6,7

椭球卷：8

什么，而不是我现在得到，这就是：

立方体的体积：[]

金字塔v olumes：6,7

椭圆形卷：8

有什么办法来实现正确的最终输出？

这是我的代码（这可能不是很大，但它是最好的，我现在可以做一个初学者，用那东西我们至今教授）：

#A program that allows the user to continuously pick different shapes and calculate their volumes. 

#import all functions from the math module. 

import math 
#allows the user to input the shape they want to calculate the volume of. Then that input is converted to all upper case 
#letters so that no matter what the user enters, it will be recognizable by the program. 
shape = input("please enter the shapes you want to calculate the volume of from cube, pyramid and ellipsoid, or Quit: ").upper() 

#Initializing the lists for the volumes of the three different shapes as empty lists so that it can be filled 
#later on. 
VolumeListCube = [] 
VolumeListPyramid =[] 
VolumeListEllipsoid = [] 

#defining the function that will calculate the volume of the cube and then adding them to the empty list VolumeListCube. 
def VolumeCube (sideLength): 
    volume = sideLength**3 
    #Adding the values to the list 
    VolumeListCube.append(volume) 
    #Sorting the values in the created list in ascending order 
    VolumeListCube.sort() 
    return; 

#defining the function that will calculate the volume of the pyramid and then adding them to the empty list VolumeListPyramid. 
def VolumePyramid (baseLength, height): 
    volume = round((1/3)*(baseLength**2)*height,1) 
    #Adding the values to the list 
    VolumeListPyramid.append(volume) 
    #Sorting the values in the created list in ascending order 
    VolumeListPyramid.sort() 
    return; 

#defining the function that will calculate the volume of the ellipsoid and then adding them to the empty list VolumeListEllipsoid. 
def VolumeEllipsoid (radius1, radius2, radius3): 
    volume = round((4/3)*math.pi*radius1*radius2*radius3,1) 
    #Adding the values to the list 
    VolumeListEllipsoid.append(volume) 
    #Sorting the values in the created list in ascending order 
    VolumeListEllipsoid.sort() 
    return; 

#The first while loop here checks if the user immediately inputs "Quit" or not, if they don't, then the next while loop is 
#executed, if they do input "Quit", then the program will print the require message. 
while shape != "QUIT": 
    #This is a infinte while loop since true is always true, this allows the error message at the end to be displayed 
    #and then loop back to the beginning of this loop, so that it can be executed again. 
    while True: 
     if shape in ["CUBE","PYRAMID","ELLIPSOID","QUIT"]: 
      #These if functions will allow the user to input shape parameters depending on what shape the user has chosen, then 
      #afterwards, another prompt is show for the user to choose another shape and input that shape's parameters. This will 
      #continue until the user inputs "Quit", then the required message will be printed and the volume results fot all the 
      #shapes chosen will be displayed in ascending order. 
      if shape == "CUBE": 
       sideLength = int(input("Please enter the length of the sides of the cube:")) 
       #recalling the function that calculates the volume of the cube. 
       VolumeCube (sideLength) 
       #lets the user to input another shape they want to calculate the volume of. 
       shape = input("please enter the shapes you want to calculate the volume of from cube, pyramid and ellipsoid, or Quit: ").upper() 
      elif shape == "PYRAMID": 
       baseLength = int(input("Please enter the base length:")) 
       height = int(input("Please enter the height:")) 
       # recalling the function that calculates the volume of the pyramid. 
       VolumePyramid (baseLength, height) 
       #lets the user to input another shape they want to calculate the volume of. 
       shape = input("please enter the shapes you want to calculate the volume of from cube, pyramid and ellipsoid, or Quit: ").upper() 
      elif shape == "ELLIPSOID": 
       radius1 = int(input("Please enter the first radius:")) 
       radius2 = int(input("Please enter the second radius:")) 
       radius3 = int(input("Please enter the third radius:")) 
       # recalling the function that calculates the volume of the ellipsoid. 
       VolumeEllipsoid (radius1, radius2, radius3) 
       #lets the user to input another shape they want to calculate the volume of. 
       shape = input("please enter the shapes you want to calculate the volume of from cube, pyramid and ellipsoid, or Quit: ").upper() 
      elif shape == "QUIT": 
       print ("\nYou have come to the end of the session.\nthe volume calculated for each shape are shown below:\n") 
       print("The volume of the cube(s) is:", VolumeListCube) 
       print("The volume of the pyramid(s) is:", VolumeListPyramid) 
       print("The volume of the ellipsoid(s) is:", VolumeListEllipsoid) 
       #This exits the program to stop repeated prints that would be caused due to the while loop 
       exit() 
     else: 
      print("Error, please enter a valid shape") 
      shape = input("please enter the shapes you want to calculate the volume of from cube, pyramid and ellipsoid, or Quit: ").upper() 

else: 
    print ("\nYou have come to the end of the session.\nYou have not performed any volume calculations") 

Answer 1

TL; DR

没有时间去通过您的代码，但我猜你所得到的最终结果为list，所以

立方体的体积：[]

对此的快速转义是使用if语句来检查列表的大小是否为0。即用户没有给出shape。

所以，一个简单的：

print('cube volumes:',end=' ') 

#VolumeListCube is holding the final results 
if len(VolumeListCube) == 0: 
    print("You have not done any calculations for the cube") 
else : 
    #print your values as usual 

应该足够了。编程