从 Python 中的合并排序函数返回的错误

Question

I have tried to write a Merge Sort function as you can see below. But when I try to test it I receive an error:

the name mergesort is not defined

Can anyone point out the cause for this error?

    def merge(self,a,b):

    sorted_list=[]

    while len(a)!=0 and len(b)!=0:

        if a[0].get_type()<b[0].get_type():
            sorted_list.append(a[0])
            a.remove(a[0])
        else:
            sorted_list.append(b[0])
            b.remove(b[0])
    if len(a)==0:
        sorted_list+=b
    else:
        sorted_list+=a

    return sorted_list

def mergesort(self,lis):

    if len(lis) == 0 or len(lis) == 1:
        return lis
    else:
        middle = len(lis)// 2
        a = mergesort(lis[middle:]) #in pycharm the next 3 lines are with red underlined
        b = mergesort(lis[middle:])
        return merge(a,b)

Answer 1

The fact that self is one of the parameters to these methods means that they're most likely part of a class (one you've omitted from your post).

If that's correct, you need to invoke using self.mergesort(l) , where l is a list.

As a pre-emptive measure against the next error you'll discover, you need to replace return merge(a, b) with return self.merge(a, b) for similar reasons.

Finally, I have to ask why you're defining all of these functions as methods of a class. They don't seem to rely on any shared data. Are you confident that they wouldn't be more appropriately declared at the module scope?