python - 如何使 IF 语句更有效？

Question

我创建了一个小程序，它接受用户输入的“飞行规范”，并根据输入输出该飞行的详细信息。然而，它只是一堆if语句，我想知道是否有任何有用的技术来减少if语句的数量并使程序更高效。
代码:

import time

def main():

    AMS_DESTINATION = "Schiphol, Amsterdam"
    GLA_DESTINATION = "Glasgow, Scotland"
    AMS_PRICE = 150.00
    GLA_PRICE = 80.00

    # User input [LLL 0 00 L L]
    flightSpecification = str(input("Enter Flight Specification: "))
    flightDestination = flightSpecification[0:3]

    bagCount = int(flightSpecification[4])
    baggageCost = float((bagCount - 1) * 20)

    passengerAge = int(flightSpecification[6:8])

    standardMeal = 10.00  
    vegetarianMeal = 12.00
    mealType = str(flightSpecification[9])

    seatClass = str(flightSpecification[11])

    totalFlightCost = 0
    
    if flightDestination.lower() != 'ams' and flightDestination.lower() != 'gla':
        print("Please enter a valid flight specification! [LLL 0 00 L L]")
        time.sleep(2)
        main()

    if flightDestination.lower() == 'ams':
        print(f"Destination: {AMS_DESTINATION}")  
        print(f"Flight cost: £{AMS_PRICE}")
        totalFlightCost = 150

    elif flightDestination.lower() == 'gla':
        print(f"Destination: {GLA_DESTINATION}")
        print(f"Flight cost: £{GLA_PRICE}")
        totalFlightCost = 80

    print(f"Number of bags: {bagCount}")
    print(f"Baggage Cost: £{baggageCost}")

    if passengerAge > 15:
        print("Child: False")
        
    elif passengerAge <= 15:
        print("Child: True")
        totalFlightCost = totalFlightCost / 2
        standardMeal = standardMeal - 2.50
        vegetarianMeal = vegetarianMeal - 2.50
        
    elif passengerAge < 0:
        print("Age cannot be negative")
        main()

    if mealType == 'S' and seatClass != 'F':
        totalFlightCost = totalFlightCost + standardMeal
        print("Meal: Standard")
        print(f"Meal Cost: £{standardMeal}")
        
    elif mealType == 'V' and seatClass != 'F':
        totalFlightCost = totalFlightCost + vegetarianMeal
        print("Meal: Vegetarian")
        print(f"Meal Cost: £{vegetarianMeal}")

    elif mealType == 'N':
        print("Meal: None")
        print("Meal Cost: £0")

    # THIS COULD DEFINITELY BE DONE MORE EFFICIENTLY
    if seatClass == 'F':
        if mealType == 'S':
            totalFlightCost = totalFlightCost + standardMeal
            print("Meal: Standard")
            print(f"Meal Cost: FREE")
            
        elif mealType == 'V':
            totalFlightCost = totalFlightCost + vegetarianMeal
            print("Meal: Vegetarian")
            print(f"Meal Cost: £{vegetarianMeal}")
            
        print("Seating Class: First")
        totalFlightCost = totalFlightCost * 6

    elif seatClass == 'E':
        print("Seating Class: Economy")

    print(totalFlightCost)
        
        

main()

谢谢

Answer 1

代码
除了您问题下方的评论外，我在您提到的可以优化的部分更改了一个小东西(我还删除了用户输入，因为它减慢了过程，最后您会明白):

import time

def main2():

    AMS_DESTINATION = "Schiphol, Amsterdam"
    GLA_DESTINATION = "Glasgow, Scotland"
    AMS_PRICE = 150.00
    GLA_PRICE = 80.00

    # User input [LLL 0 00 L L]
    # flightSpecification = str(input("Enter Flight Specification: "))
    flightSpecification = 'AMS 1 22 V F'
    flightDestination = flightSpecification[0:3]

    bagCount = int(flightSpecification[4])
    baggageCost = float((bagCount - 1) * 20)

    passengerAge = int(flightSpecification[6:8])

    standardMeal = 10.00  
    vegetarianMeal = 12.00
    mealType = str(flightSpecification[9])

    seatClass = str(flightSpecification[11])

    totalFlightCost = 0
    
    if flightDestination.lower() != 'ams' and flightDestination.lower() != 'gla':
        print("Please enter a valid flight specification! [LLL 0 00 L L]")
        time.sleep(2)
        main()

    if flightDestination.lower() == 'ams':
        print(f"Destination: {AMS_DESTINATION}")  
        print(f"Flight cost: £{AMS_PRICE}")
        totalFlightCost = 150

    elif flightDestination.lower() == 'gla':
        print(f"Destination: {GLA_DESTINATION}")
        print(f"Flight cost: £{GLA_PRICE}")
        totalFlightCost = 80

    print(f"Number of bags: {bagCount}")
    print(f"Baggage Cost: £{baggageCost}")

    if passengerAge > 15:
        print("Child: False")
        
    elif passengerAge <= 15:
        print("Child: True")
        totalFlightCost = totalFlightCost / 2
        standardMeal = standardMeal - 2.50
        vegetarianMeal = vegetarianMeal - 2.50
        
    elif passengerAge < 0:
        print("Age cannot be negative")
        main()

    if mealType == 'S' and seatClass != 'F':
        totalFlightCost = totalFlightCost + standardMeal
        print("Meal: Standard")
        print(f"Meal Cost: £{standardMeal}")
        
    elif mealType == 'V' and seatClass != 'F':
        totalFlightCost = totalFlightCost + vegetarianMeal
        print("Meal: Vegetarian")
        print(f"Meal Cost: £{vegetarianMeal}")

    elif mealType == 'N':
        print("Meal: None")
        print("Meal Cost: £0")

    # THIS COULD DEFINITELY BE DONE MORE EFFICIENTLY
    if seatClass == 'F' and mealType is 'S':
        totalFlightCost = totalFlightCost + standardMeal
        print("Meal: Standard")
        print(f"Meal Cost: FREE")

        print("Seating Class: First")
        totalFlightCost = totalFlightCost * 6
            
    elif seatClass is 'F' and mealType == 'V':
        totalFlightCost = totalFlightCost + vegetarianMeal
        print("Meal: Vegetarian")
        print(f"Meal Cost: £{vegetarianMeal}")
            
        print("Seating Class: First")
        totalFlightCost = totalFlightCost * 6

    elif seatClass == 'E':
        print("Seating Class: Economy")

    print(totalFlightCost)

测试
更改 main 中的输入，您将在下面的测试中认识到没有真正的性能问题:

start = time.time()
main()
print('main() takes: ')
print(time.time() - start)

start = time.time()
main2()
print('main2() takes:') 
print(time.time() - start)

结果
main() 需要:
7.319450378417969e-05 秒
main2() 需要:
4.935264587402344e-05 秒
值得一提
在您设置的递归路径中(在评论中提到)，您还使用 time.sleep(2)。插入硬编码 sleep 总是会影响你的表现。