if else语句上的python 3.5.1语法错误[重复]

Question

我正在做一个家庭作业，它看起来像这样：

def main():
    keep_going = 'y'
    number_of_salespeople = 0

    while keep_going == 'y' or keep_going == 'Y':
        process_sales()
        number_of_salespeople += 1
        keep_going = input('Are there more salespeople? (enter y or Y for yes) ')

    print(' ')
    print('There were', number_of_salespeople, 'salespeople today.')

def process_sales():        
    print(' ')
    name = input('What is the salesperson\'s name? ')

    first_sale_amount = float(input('What is', name, '\'s first sale amount? '))
    while 0 <= first_sale_amount <= 25000:
        print('Error: that is not a valid sales amount. The amount must be greater than 0')
        first_sale_amount = float(input('Please enter a correct sale amount: '))

    highest_sale = first_sale_amount
    lowest_sale = first_sale_amount
    average_sale = first_sale_amount

    number_of_sales = float(input('How many sales did', name, 'make this month? '))

    for number in range(2, number_of_sales + 1):
        sale_amount = float(input('Enter', name, '\'s time for sale #' + str(number) + ': '))
        while 0 <= sale_amount <= 25000:
            print('Error: that is not a valid sales amount. The amount must be greater than 0')
            sale_amount = float(input('Please enter a correct sale amount: '))

    if sale_amount > highest_sale:
        highest_sale = sale_amount

    else sale_amount < lowest_sale:
        lowest_sale = sale_amount

    total_sales += sale_amount
    average_sale = (first_sale_amount + total_sales) / number_of_sales

    print('The highest sale for', name, 'was', \
          format(highest_sale, ',.2f'), \
          sep='')

    print('The lowest sale for', name, 'was', \
          format(lowest_sale, ',.2f'), \
          sep='')

    print('The average sale for', name, 'was', \
          format(average_sale, ',.2f'), \
          sep='')

main()

我遇到的错误是在底部的 if else 语句中，

if sale_amount > highest_sale:
    highest_sale = sale_amount

else sale_amount < lowest_sale:
    lowest_sale = sale_amount

错误如下所示：

语法错误：否则 sale_amount

我看不出问题出在哪里，谁能帮我找出错误的来源。感谢您的帮助。

Answer 1

你应该先学习python的基本语法。看看python中的if and elif。

elif 部分可以有零个或多个，else 部分是可选的。 关键字elif 是else if 的缩写，有助于避免 缩进过多。

所以在第一个if 之后检查更多条件，你需要这样的东西：

if cond1:
   # do something
elif cond2:
   # do something else
# more elif branches if needed, and finally else if there is something default
else:
   # do the default thing

---

您的代码还有更多问题。

1.input 错误，因为传递了多个参数。您可以像这样使用字符串的format 方法：

first_sale_amount = float(input("What is {}'s first sale amount?".format(name)))

2.while中的条件逻辑错误。如果要检查输入的值是否在 0-25000（含）范围内 not，则应在条件前添加 not，如下所示：

while not 0 <= first_sale_amount <= 25000:
        print('Error: that is not a valid sales amount. The amount must be greater than 0')
        first_sale_amount = float(input('Please enter a correct sale amount: '))

可能还有 3、4、5 等等。

Answer 2

else 不能有条件。改为elif（“else if”）。