停止for循环，只是变为true或false

Question

我为我的问题制作了这个示例代码。 我需要离开True或False然后停止循环，但我不知道怎么办？

def test():
    list = [u"sam", u"jay", u"jean", u"smo", u"gon", u"bil"]
    user = u"jean"
    for x in list:
        if user==x:
            print True
        else:
            print False
test()

输出：

False
False
True
False
False
False

Answer 1

您可以使用in：

def test():
    users = [u"sam", u"jay", u"jean", u"smo", u"gon", u"bil"]
    user = u"jean"
    return user in users

演示：

>>> users = [u"sam", u"jay", u"jean", u"smo", u"gon", u"bil"]
>>> user = u"jean"
>>> user in users
True

请注意，list不是一个好的变量名，因为它会内置list。

---

如果您需要for循环，则在点击匹配时需要break循环，else block of the for loop中需要print False：

def test():
    users = [u"sam", u"jay", u"jean", u"smo", u"gon", u"bil"]
    user = u"jean"
    for x in users:
        if user == x:
            print True
            break
    else:
        print False

Answer 2

虽然alecxe有最佳答案，但还有一个选择：变量！

def test():
    users = [u"sam", u"jay", u"jean", u"smo", u"gon", u"bil"]
    user = u"jean"

    found = False
    for x in users:
        if user == x:
            found = True;

    print found

Answer 3

def test():
    list = [u"sam", u"jay", u"jean", u"smo", u"gon", u"bil"]
    user = u"jean"
    for x in list:
        if user==x:
            print True
            break
        else:
            print False
test()

您可以使用break来提前退出循环。

Answer 4

def test():
    list = [u"sam", u"jay", u"jean", u"smo", u"gon", u"bil"]
    user = u"jean"
    for x in list:
        if user==x:
            print True
            return # or return True depending on how you want it to work
                   # break might also be of value here
        else:
            print False
test()