1

一个非常简单的while循环语句会继续下面的程序，直到用户键入“exit”？

例如，

while response = (!'exit')
    continue file
else
    break
    print ('Thank you, good bye!')
#I know this is completely wrong, but it's a try!

到目前为止我的文件：

#!/usr/bin/python
friends = {'John' : {'phone' : '0401',
        'birthday' : '31 July',
        'address' : 'UK',
        'interests' : ['a', 'b', 'c']},
    'Harry' : {'phone' : '0402',
        'birthday' : '2 August',
        'address' : 'Hungary',
        'interests' : ['d', 'e', 'f']}}
response = raw_input("Please enter search criteria, or type 'exit' to exit the program: ").split()
try:
    print "%s's %s is %s" % (response[0], response[1], friends[response[0]][response[1]])
except KeyError:
    print "Sorry, I don't know about that. Please try again, or type 'exit' to leave the program: "
4

3 回答 3

4

continue是一个不需要参数的关键字。它只是告诉当前循环立即继续到下一次迭代。它可以在while和for循环内部使用。

Your code should then be placed within the while loop, which will keep going until the condition is met. Your condition syntax is not correct. It should read while response != 'exit':. Because you are using a condition, the continue statement is not needed. It will by design continue as long as the value is not "exit".

Your structure would then look like this:

response = ''
# this will loop until response is not "exit"
while response != 'exit':
    response = raw_input("foo")

If you wanted to make use of continue, it might be used if you were going to do other various operations on the response, and might need to stop early and try again. The break keyword is a similar way to act on the loop, but it instead says we should immediately end the loop completely. You might have some other condition that is a deal breaker:

while response != 'exit':
    response = raw_input("foo")

    # make various checks on the response value
    # obviously "exit" is less than 10 chars, but these
    # are just arbitrary examples
    if len(response) < 10:
        print "Must be greater than 10 characters!"
        continue  # this will try again 

    # otherwise
    # do more stuff here
    if response.isdigit():
        print "I hate numbers! Unacceptable! You are done."
        break
于 2012-05-05T01:44:18.397 回答
3

您的 while 循环将继续，直到您设置的条件为假。所以你希望你的代码大部分都在这个循环中。完成后，您知道用户输入了“退出”，因此您可以打印错误消息。

#!/usr/bin/python
friends = {'John' : {'phone' : '0401',
        'birthday' : '31 July',
        'address' : 'UK',
        'interests' : ['a', 'b', 'c']},
    'Harry' : {'phone' : '0402',
        'birthday' : '2 August',
        'address' : 'Hungary',
        'interests' : ['d', 'e', 'f']}}

response = ['']
error_message = "Sorry, I don't know about that. Please try again, or type 'exit' to leave the program: "

while response[0] != 'exit':
    response = raw_input("Please enter search criteria, or type 'exit' to exit the program: ").split()
    try:
        print "%s's %s is %s" % (response[0], response[1], friends[response[0]][response[1]])
    except KeyError:
        print error_message
    except IndexError:
        print error_message

print ('Thank you, good bye!')

这段代码是你想要的开始，但它仍然有一些错误。看看您是否可以对其进行重组，以便在用户输入“退出”时不打印错误消息。

于 2012-05-05T01:37:54.153 回答
3 
#!/usr/bin/python
friends = {
    'John' : {
        'phone' : '0401',
        'birthday' : '31 July',
        'address' : 'UK',
        'interests' : ['a', 'b', 'c']
    },
    'Harry' : {
        'phone' : '0402',
        'birthday' : '2 August',
        'address' : 'Hungary',
        'interests' : ['d', 'e', 'f']
    }
}

def main():
    while True:
        res = raw_input("Please enter search criteria, or type 'exit' to exit the program: ")
        if res=="exit":
            break
        else:
            name,val = res.split()
            if name not in friends:
                print("I don't know anyone called {}".format(name))
            elif val not in friends[name]:
                print("{} doesn't have a {}".format(name, val))
            else:
                print("{}'s {} is {}".format(name, val, friends[name][val]))

if __name__=="__main__":
    main()
于 2012-05-05T02:01:31.367 回答