为什么python告诉我我的yes变量没有定义

Question

我用Python 2.7:编写了这个脚本

name=raw_input("Hi im a PC, who are you?")
print("Hi " + name + " how are you, are you good?")
answer = raw_input("")
if (answer) == yes:
    print("That's good to hear")
elif (answer) == no:
    print("Oh well")
else:
    print("Sorry, you didnt answer the question properly, Please answer with a yes or no")

这是我得到的错误：

追踪（最近一次通话）：文件"C:\Python27/programs/2"，第4行，位于如果（答案）==是：NameError:未定义名称"yes"

Answer 1

您没有名为yes的变量，
您要做的是将用户输入与字符串"yes" 进行比较

哪个会像：

if answer == "yes":
    # do stuff

答案周围也不需要括号。

Answer 2

answer是一个字符串，您应该使用answer == "yes"

Answer 3

您需要在字符串中放入"或'。yes不是"yes"并且no不是"no"。

#if (answer) == yes:
if (answer) == "yes":
#elif (answer) == no:
elif (answer) == "no":

错误name 'yes' is not defined是因为解释器查找名为yes的变量，因为该单词没有"或'。如果您编写"yes"，解释器将比较answer变量的值和字符串"yes"。