Python總是得到相同的結果

Question

我在下面編寫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.

這是我編寫的代碼-基於我之前編寫的Java程序，顯然不適合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!')

無論輸入什么顏色組合，都會得到“紫色”的結果。 該程序的邏輯哪里出了問題？ 此外，當我不輸入綠色作為原色時，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

而不是錯誤消息“您沒有輸入原色！”

我要去哪里錯了？

編輯：這是我的新代碼，除了錯誤輸出外，它還可以工作。

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

您的麻煩在於以下幾行：

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

執行此操作時，輸入的任何非空值都將導致True 。 您能夠獲得False的唯一方法是在提示符后按return並提交一個空字符串。 您想要處理用戶輸入內容的邏輯有些缺陷。 你可能想要：

if color1 == 'red'

在您刪除了多余的bool調用之后，但這只是一個建議。

Answer 2

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

如果我們簡化一下，我們得到

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

因此，現在您的比較正在評估False等於True完全忽略了您輸入的顏色。

嘗試類似

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

您的代碼有一些大問題。 首先，您調用bool(input()) 。 只要你提供一些輸入， color1和/或color2被設置為True。

因此，您在調用if True == False ...您的代碼不執行任何操作來檢查顏色的實際名稱。 相反，我建議使用普通的input()接受` string 。

這是您編輯的代碼：

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

你應該比較color1和color2為字符串不是布爾值：

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

問題似乎出在這些方面

red = False
blue = False
yellow = False

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

輸入顏色時，無論顏色是哪種，它都將被設置為false。 在計算機上正在發生（我將使用紅色和黃色作為示例）

color1 = bool(red)

由於您之前將紅色定義為False：

color1 = bool(False)
color1 = False

相似地

color2 = bool(yellow)

黃色也被定義為False

color2 = bool(False)
color2 = False

因此，當我們到達您的第一個if語句時

if color1 == red and color2 == blue:

電腦看到

if False==False and False == False:

評估為True

if True and True:
if True:

您使用部分input（）可能會導致部分問題。 對於python2.x（我會假設您正在使用），input（）會評估輸入的內容。 例如：

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

將分別返回整數值3和浮點值3.1。 計算機會查看您鍵入的內容，並盡力為您提供有意義的數據。 就你而言。

yellow = False

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

>>>yellow

計算機將在程序的名稱空間中搜索黃色表達式的值，該表達式在該程序中為False。

它可以幫助您使用raw_input（），它不評估所鍵入的內容，而只是返回所鍵入內容的字符串值。 例如：

input()
>>>yellow

將評估為False，但

raw_input()
>>>yellow

將評估為字符串值“ yellow”

嘗試將顏色常量定義為字符串而不是布爾值，並將輸入也處理為字符串。 所以

yellow = "yellow"

而不是

yellow = False

Answer 6

我沒有為顏色使用變量...我只是測試了變量是否為=='color'

所以我的代碼是

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.")