Question

我正在学习如何用Python编程并且坚持这个简单的练习。我将下面的代码保存到一个文件test.py并使用“python test.py”从我的OSX命令行运行它并继续收到我无法理解的错误消息。我猜这个错误是一个被忽视的相当明显的事情：P

错误消息在代码后面：

def hotel_cost(nights):
  return 140 * nights

def plane_ride_cost(city):
  if city == "Charlotte":
    return 183
  elif city == "Tampa":
    return 220
  elif city == "Pittsburgh":
    return 222
  elif city == "Los Angeles":
    return 475

def rental_car_cost(days):
  total = 40 * days
  if days >= 7:
    total = total - 50
  elif days >= 3:
    total = total - 20
  return total

def trip_cost(city, days, spending_money):
  return rental_car_cost(days) + hotel_cost(days) + plane_ride_cost(city) + 
  spending_money

thecity = raw_input("What city will you visit? ")
thedays = raw_input("How many days will you be traveling? ")
thespending_money = raw_input("How much spending money will you have? ")

trip_cost(thecity, thedays, thespending_money)

控制台错误消息：

$ python test.py
What city will you visit? Los Angeles
How many days will you be traveling? 5
How much spending money will you have? 600
Traceback (most recent call last):
File "test.py", line 29, in <module>
  trip_cost(thecity, thedays, thespending_money)
File "test.py", line 23, in trip_cost
  return rental_car_cost(days) + hotel_cost(days) + plane_ride_cost(city) + spending_money
File "test.py", line 17, in rental_car_cost
  total = total - 50
TypeError: unsupported operand type(s) for -: 'str' and 'int'

Answer 1

将thedays = raw_input("How many days will you be traveling? ")更改为thedays = input("How many days will you be traveling? ")，并在需要数字值时将所有其他raw_input替换为input。

Answer 2

thecity = raw_input("What city will you visit? ")＆＃34;城市n＃34;是一个字符串。使用int：

从字符串生成整数

thecity = int(raw_input("What city will you visit? "))

与其他输入类似。

Answer 3

thedays = raw_input("How many days will you be traveling? ")

raw_input返回一个字符串。因此，当您输入5时，您会获得字符串 '5'而不是整数 5。当您尝试添加Python时，Python不会自动为您转换这些内容，因为在某些情况下，这会导致更大的意外。相反，它希望您明确地进行转换，以便在任何输入的情况下，您的代码始终是明确的（例如，“将字符串'abc'解析为基本10整数”是总是错误;尝试通过隐式转换执行"abc" + 5可能会决定将5转换为字符串'5'并进行字符串连接以提供"abc5"）。

执行此操作的方法是使用内置int，它接受一个字符串并返回一个从中解析的整数：

thedays = int(raw_input("How many days will you be traveling? "))

无法让这个简单的python程序工作

3 个答案: