多功能python编程

Question

我试图编写一个程序，要求用户输入两种颜色，然后显示结果的颜色。到目前为止，这就是我所拥有的：

#Define function that prompts user to enter data
def ask():
    color1=input('Enter name of first primary color:')
    color2=input('Enter name of second primary color:')
    mixColors(color1,color2)
#Write function that displays the different color combinations
def mixColors(color1,color2):
    if color1==red and color2==blue:
        print('Mixing red and blue, you get purple.')
    elif color1==blue and color2==red:
        print('Mixing blue andred, you get purple.')
    elif color1==red and color2==yellow:
        print('Mixing red and yellow, you get orange.')
    elif color1==yellow and color2==red:
        print('Mixing yellow and red, you get orange.')
    elif color1==blue and color2==yellow:
        print('Mixing blue and yellow you get green.')
    elif color1==yellow and color2==blue:
        print('Mixing yellow and blue, you get green.')
    else:
        print("I don't know what you get by mixing", color1,'and',color2,'.')
ask()

当我运行程序时，会出现以下错误消息：

Traceback (most recent call last):
  File "/Users/Lin/Documents/Spring Semester 2013/Computer Programming/yuan_linCh0405", line 23, in <module>
    ask()
  File "/Users/Lin/Documents/Spring Semester 2013/Computer Programming/yuan_linCh0405", line 6, in ask
    mixColors(color1,color2)
  File "/Users/Lin/Documents/Spring Semester 2013/Computer Programming/yuan_linCh0405", line 9, in mixColors
    if color1==red and color2==blue:
NameError: global name 'red' is not defined

Answer 1

在Python中，字符串必须用单引号或双引号('或")括起来。否则，它们将被视为变量。

在这种情况下，red既不是变量也不是字符串。因为red不是字符串，所以它在当前名称空间、父名称空间和全局命名空间中搜索red。但是变量red在其中任何一个中都找不到。因此，它放弃并抛出错误消息。

所以，所有的条件都应该是

if color1=="red" and color2=="blue":
...
elif color1=="blue" and color2=="red":
...
elif color1=="red" and color2=="yellow":
...
elif color1=="yellow" and color2=="red":
...
elif color1=="blue" and color2=="yellow":
...
elif color1=="yellow" and color2=="blue":
...