追溯（最近一次呼叫过去）：和TypeError：

Question

I'm still very much a beginner with Python and I'm using codecademy at the minute. I decided to complicate one of the practice programs slightly and I've come across this error:

Traceback (most recent call last):
File "python", line 30, in <module>
File "python", line 24, in trip_cost
File "python", line 18, in rental_car_cost
TypeError: unsupported operand type(s) for -: 'unicode' and 'int'

Here is my code:

def hotel_cost(nights):
  # the hotel costs $140 per night
  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):
  cost = days * 40
  if days >= 7:
    cost -= 50
  elif days >= 3 and days < 7:
    cost -= 20
  return cost

def trip_cost(city, days, spending_money):
  return rental_car_cost(days) + hotel_cost(days - 1) + plane_ride_cost(city) + spending_money

x = raw_input("Where are you going? ")
y = raw_input("How many days are you going for? ")
z = raw_input("How much spending money are you taking? ")

print trip_cost(x, y, z)

Any help would be much appreciated, thanks! I'm a beginner so my python lingo is a bit rusty.

Answer 1

You're doing days - 1 or cost -= 50 but days and cost are user inputs and therefore a string (unicode string more accurately in your case), you should convert to int before doing anything (especially math) since that's your intention:

y = int(raw_input("How many days are you going for? "))
z = int(raw_input("How much spending money are you taking? "))

This is because you are using them as if they're numbers without converting

However be warned, inputting in anything other then numbers will generate errors, but that's the subject for another question