不知道为什么这段代码会导致语法错误，有人知道为什么吗？
# Ask for user input
choice = input ("Enter the letter A or B: ")
# Detect choice
if choice == A:
print ("You entered A!")
elif choice == B:
print ("You enetered B")
else:
print ("You didn't enter A or B!")
You try to tell him
if choice == A. This means that A is a variable, and if A is not defined, it will not work ! You forgot to put 2 " to make it a string, and then to be able to compare it. So now your code looks like:由于输入存储为字符串，因此需要将其与字符串进行比较：
您必须写“ A”和“ B”而不是A和B。引号之间的单词是一个字符串，没有引号的是变量。您写入选择变量的是一个字符串