我在理解为什么有些变量是局部变量而有些变量是全局变量时遇到了一些困难。例如。当我尝试这个时:
from random import randint
score = 0
choice_index_map = {"a": 0, "b": 1, "c": 2, "d": 3}
questions = [
"What is the answer for this sample question?",
"Answers where 1 is a, 2 is b, etc.",
"Another sample question; answer is d."
]
choices = [
["a) choice 1", "b) choice 2", "c) choice 3", "d) choice 4"],
["a) choice 1", "b) choice 2", "c) choice 3", "d) choice 4"],
["a) choice 1", "b) choice 2", "c) choice 3", "d) choice 4"]
]
answers = [
"a",
"b",
"d"
]
assert len(questions) == len(choices), "You haven't properly set up your question-choices."
assert len(questions) == len(answers), "You haven't properly set up your question-answers."
def askQ():
# global score
# while score < 3:
question = randint(0, len(questions) - 1)
print questions[question]
for i in xrange(0, 4):
print choices[question][i]
response = raw_input("> ")
if response == answers[question]:
score += 1
print "That's correct, the answer is %s." % choices[question][choice_index_map[response]]
# e.g. choices[1][2]
else:
score -= 1
print "No, I'm sorry -- the answer is %s." % choices[question][choice_index_map[answers[question]]]
print score
askQ()
我收到此错误:
Macintosh-346:gameAttempt Prasanna$ python qex.py
Answers where 1 is a, 2 is b, etc.
a) choice 1
b) choice 2
c) choice 3
d) choice 4
> b
Traceback (most recent call last):
File "qex.py", line 47, in <module>
askQ()
File "qex.py", line 39, in askQ
score += 1
UnboundLocalError: local variable 'score' referenced before assignment
现在,我完全明白为什么它会让我得分失误了。我没有在全球范围内设置它(我故意注释掉该部分以显示这一点)。而且我特别不使用 while 子句来让它继续前进(否则它甚至不会进入该子句)。让我困惑的是为什么它不会给我同样的问题、选择和答案错误。当我取消注释掉这两行时,脚本运行得非常好——即使我没有将问题、答案和选择定义为全局变量。这是为什么?这是我在搜索其他问题时未能发现的一件事——Python 似乎不一致。这与我使用列表作为其他变量有关系吗?这是为什么?
(另外,第一次发帖;非常感谢我在不需要提问的情况下发现的所有帮助。)