如何在python中对计算器进行输入检查？答案

【问题标题】：How to put an input check for a calculator in python?如何在python中对计算器进行输入检查？
【发布时间】：2020-08-29 11:21:59
【问题描述】：

print("Welcome to the Kinetic Energy and Gravitational Potential Energy Calculator")
print("Which Calculator would you like to access?")

Choice = str(input("Type in KE for Kinetic Energy and GPE for Gravitational Potential Energy:"))

while Choice != "KE" or "GPE":
    print("Error. You have not entered a valid choice. Please type KE or GPE.")
    Choice = str(input("Type in KE for Kinetic Energy and GPE for Gravitational Potential Energy:"))


while Choice == "KE":
    print("You have chosen the Kinetic Energy Calculator.")
    mass = float(input("Type in the mass of the object in kilograms (kg):"))
    velocity = float(input("Type in the velocity of the object in metres per second (m/s):"))
    result = 0.5*mass*(velocity**2)
    print("The KE is:", result, "J(Joules)")
    Choice = str(input("Type in KE for Kinetic Energy and GPE for Gravitational Potential Energy:"))

while Choice == "GPE":
    print("You have chosen the Gravitational Potential Energy Calculator.")
    mass = float(input("Type in the mass of the object in kilograms (kg):"))
    height = float(input("Type in the height at which the object is in metres (m):"))
    result = 9.81*mass*height
    print("The GPE is:", result, "J(Joules)")
    Choice = str(input("Type in KE for Kinetic Energy and GPE for Gravitational Potential Energy:"))

我尝试过使用“或”，所以检查可以同时包含“KE”和“GPE”，但是当你运行程序时，即使我输入了 KE 或 GPE，第一个 while 循环也会继续进行！我怎样才能让它发挥作用？

【问题讨论】：

标签： python input while-loop calculator

【解决方案1】：

问题在于你的情况。由于"GPE"在逻辑上是True（非空字符串在逻辑上是True），所以while循环条件总是True，不管选择什么。

变化：

Choice != "KE" or "GPE"

到：

Choice != "KE" and Choice != "GPE"

或：

Choice not in ["KE","GPE"]

【讨论】：