具有多种功能的python编程

Question

我正在尝试编写一个程序，要求用户输入两种颜色，然后显示结果颜色。这是我目前所拥有的:

#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()

当我运行该程序时，出现此错误消息:

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括起来(' 或 ")。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。由于 red 不是字符串，Python 在当前命名空间、父命名空间和全局命名空间中搜索 red。但是在其中任何一个中都找不到变量 red 。因此，它放弃并抛出该错误消息。

所以，所有的if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":
...