Python速度違規計算器返回TypeError錯誤

Question

我有一些問題，同時調試一個程序，我正在設計採取整數用戶輸入的速度限制和車輛的速度，在我的violationCalculator計算之前，用戶多少正在超速。

我得到一個TypeError: unsupported operand type(s) for -: 'NoneType' and 'int'，這是引用speedExcess = driverSpeed - designatedLimit，與violationCalculator 舉行。

我有查明我已經錯了，希望得到一些指導的問題 -

def speedLimit(): 
    designatedLimit = int(input("Please enter the designated speed limit: ")) 
    while designatedLimit not in range(20, 70): 
     print("Invalid entry: please enter a valid speed limit (20-70)") 
     designatedLimit = int(input("Please enter the designated speed limit: ")) 
    return designatedLimit 

def vehicleSpeed(designatedLimit): 
    driverSpeed = int(input("Please enter the vehicle's speed: ")) 
    while driverSpeed <= designatedLimit: 
     print("You were not speeding!") 
     driverSpeed = int(input("Please enter a valid vehicle speed: ")) 
     return driverSpeed 

def violationCalculator(designatedLimit, driverSpeed): 
    speedExcess = driverSpeed - designatedLimit 
    return speedExcess 

def main(): 
    welcomeSplash() 
    designatedLimit = speedLimit() 
    driverSpeed = vehicleSpeed(designatedLimit) 
    speedExcess = violationCalculator(designatedLimit, driverSpeed) 
    print("If you were travelling at", driverSpeed, "in a", designatedLimit, 
    "zone, then you were over the designated speed limit by", speedExcess) 
main() 

Answer 1

這只是壓痕問題。你是不是因爲回報有時返回任何東西在裏面，而

def vehicleSpeed(designatedLimit): 
    driverSpeed = int(input("Please enter the vehicle's speed: ")) 
    while driverSpeed <= designatedLimit: 
     print("You were not speeding!") 
     driverSpeed = int(input("Please enter a valid vehicle speed: ")) 
    return driverSpeed 

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