Python保持输出“无”

Question

每当我尝试运行此代码时：

def isPalindrome( theSubList ):
    theSubListtest = theSubList[0:]
    if len(theSubListtest) <= 1:
        return True
    elif len(theSubListtest) == 2:
        x = theSubListtest[0]
        y = theSubListtest[1]
        if (x == y):
            return True
        else:
            return Falsefirst == theSubListtest.pop(0)
    elif len(theSubListtest) > 2:
        first = theSubListtest.pop(0)
        last = theSubListtest.pop()
        if first == last:
            isPalindrome(theSubListtest)
        else:
            return False

candidatePs = [ 
    [1,], 
    range(8), 
    range(4) + range(3,-1,-1), 
    range(4) + [0] + range(3,-1,-1),
    range(3) + range(4) + [0] + range(3,-1,-1),
]

for p in candidatePs :
    print p, isPalindrome( p )

它为p的前两个值正确运行，但是对于以下三个值输出“None”。任何帮助是极大的赞赏。提前谢谢。

Answer 1

糟糕。

if (first == last):
    return isPalindrome(theSubListtest)
else:
    return False

Answer 2

你忘记了回归。改变这些行：

if (first == last):
    isPalindrome(theSubListtest)

到

if (first == last):
    return isPalindrome(theSubListtest)

并且代码将按预期工作。