Python总是得到相同的结果

Question

我在下面编写的程序具有以下要求：

# Design a program that prompts the user to enter the names of two primary colors
# to mix.  If the user enters anything other than red, blue or yellow, the
# program should display an error message.  Otherwise the program should display 
# the name of the secondary color that results.

这是我编写的代码-基于我之前编写的Java程序，显然不适合Python。

print('You will be mixing two primary colors to get a resulting color.')
print('Primary colors are blue, red and yellow \n')

red = False
blue = False
yellow = False

color1 = bool(input('Enter your first primary color: \n'))
color2 = bool(input('Enter your second primary color: \n'))

if color1 == red and color2 == blue:
        print('That makes purple!')

elif color1 == blue and color2 == red:
        print('That makes purple!')

elif color1 == yellow and color2 == red:
    print('That makes orange!')

elif color1 == red and color2 == yellow:
    print('That makes orange!')

elif color1 == blue and color2 == yellow:
    print('That makes green!')

elif color1 == yellow and color2 == blue:
    print('That makes green!')

else:
    print('You did not enter a primary color!')

无论输入什么颜色组合，都会得到“紫色”的结果。 该程序的逻辑哪里出了问题？ 此外，当我不输入绿色作为原色时，我得到以下信息：

Traceback (most recent call last):
File "color.py", line 19, in <module>
color1 = bool(input('Enter your first primary color: \n'))
File "<string>", line 1, in <module>
NameError: name 'green' is not defined

而不是错误消息“您没有输入原色！”

我要去哪里错了？

编辑：这是我的新代码，除了错误输出外，它还可以工作。

print('You will be mixing two primary colors to get a resulting color.')
print('Primary colors are blue, red and yellow \n')

red = 1
blue = 2
yellow = 3

color1 = input('Enter your first primary color: \n')
color2 = input('Enter your second primary color: \n')

if color1 == 1 and color2 == 2:
    print('That makes purple!')

elif color1 == 2 and color2 == 1:
    print('That makes purple!')

elif color1 == 3 and color2 == 1:
print('That makes orange!')

elif color1 == 1 and color2 == 3:
print('That makes orange!')

elif color1 == 2 and color2 == 3:
print('That makes green!')

elif color1 == 3 and color2 == 2:
print('That makes green!')

else:
print('You did not enter a primary color!')

Answer 1

您的麻烦在于以下几行：

color1 = bool(input('Enter your first primary color: \n'))
color2 = bool(input('Enter your second primary color: \n'))

执行此操作时，输入的任何非空值都将导致True 。 您能够获得False的唯一方法是在提示符后按return并提交一个空字符串。 您想要处理用户输入内容的逻辑有些缺陷。 你可能想要：

if color1 == 'red'

在您删除了多余的bool调用之后，但这只是一个建议。

Answer 2

color1 = bool(input('Enter your first primary color: \n'))

如果我们简化一下，我们得到

color1 = bool("red") #color1 becomes True

因此，现在您的比较正在评估False等于True完全忽略了您输入的颜色。

尝试类似

RED = 'red'
BLUE = 'blue'

color1 = input('Enter your first primary color: \n').lower()
color2 = input('Enter your second primary color: \n').lower()

if color1 == RED and color2 == BLUE:
    print('That makes purple!')

Answer 3

您的代码有一些大问题。 首先，您调用bool(input()) 。 只要你提供一些输入， color1和/或color2被设置为True。

因此，您在调用if True == False ...您的代码不执行任何操作来检查颜色的实际名称。 相反，我建议使用普通的input()接受` string 。

这是您编辑的代码：

print('You will be mixing two primary colors to get a resulting color.')
print('Primary colors are blue, red and yellow \n')

color1 = input('Enter your first primary color: \n')
color2 = input('Enter your second primary color: \n')

if color1 == 'red' and color2 == 'blue':
        print('That makes purple!')

elif color1 == 'blue' and color2 == 'red':
        print('That makes purple!')

elif color1 == 'yellow' and color2 == 'red':
    print('That makes orange!')

elif color1 == 'red' and color2 == 'yellow':
    print('That makes orange!')

elif color1 == 'blue' and color2 == 'yellow':
    print('That makes green!')

elif color1 == 'yellow' and color2 == 'blue':
    print('That makes green!')

else:
    print('You did not enter a primary color!')

Answer 4

你应该比较color1和color2为字符串不是布尔值：

color1 = input('Enter your first primary color: \n')
color2 = input('Enter your second primary color: \n')
if color1 == "red" and color2 == "blue":
    print("That makes purple!")

Answer 5

问题似乎出在这些方面

red = False
blue = False
yellow = False

color1 = bool(input('Enter your first primary color: \n'))
color2 = bool(input('Enter your second primary color: \n'))

输入颜色时，无论颜色是哪种，它都将被设置为false。 在计算机上正在发生（我将使用红色和黄色作为示例）

color1 = bool(red)

由于您之前将红色定义为False：

color1 = bool(False)
color1 = False

相似地

color2 = bool(yellow)

黄色也被定义为False

color2 = bool(False)
color2 = False

因此，当我们到达您的第一个if语句时

if color1 == red and color2 == blue:

电脑看到

if False==False and False == False:

评估为True

if True and True:
if True:

您使用部分input（）可能会导致部分问题。 对于python2.x（我会假设您正在使用），input（）会评估输入的内容。 例如：

input("Enter Something")
>>>3
input("Enter Something Else")
>>>3.1

将分别返回整数值3和浮点值3.1。 计算机会查看您键入的内容，并尽力为您提供有意义的数据。 就你而言。

yellow = False

color1 = bool(input('Enter your first primary color: \n'))

>>>yellow

计算机将在程序的名称空间中搜索黄色表达式的值，该表达式在该程序中为False。

它可以帮助您使用raw_input（），它不评估所键入的内容，而只是返回所键入内容的字符串值。 例如：

input()
>>>yellow

将评估为False，但

raw_input()
>>>yellow

将评估为字符串值“ yellow”

尝试将颜色常量定义为字符串而不是布尔值，并将输入也处理为字符串。 所以

yellow = "yellow"

而不是

yellow = False

Answer 6

我没有为颜色使用变量...我只是测试了变量是否为=='color'

所以我的代码是

color1=input('Enter primary color:')
color2=input('Enter primary color:')


if color1=='red' and color2=='blue':
    print("When you mix red and blue, you get purple.")
elif color1=='red' and color2=='yellow':
    print("When you mix red and yellow, you get orange.")
elif color1=='blue' and color2=='red':
    print("When you mix blue and red, you get purple.")
elif color1=='blue' and color2=='yellow':
    print("When you mix blue and yellow, you get green.")
elif color1=='yellow' and color2=='red':
    print("When you mix yellow and red, you get orange.")
elif color1=='yellow' and color2=='blue':
    print("When you mix yellow and blue, you get green.")
else:
    print("You didn't input two primary colors.")