为什么这个搜索功能没有返回值？

Question

我的儿子正在教自己Python，但是让我难以理解以下内容。为什么此类的搜索功能返回None？

我们显然正在点击return，因为没有它，函数会无限期地递归，并且在打印的self.found值之上的行上是正确的。

class Search:
    def __init__(self):
        print("made")
        self.n = 0
        self.found = []
    def search(self, Object, List):
        if self.n == 0:
            self.found.clear()
            print("1:self.found =", self.found, "\nself.n =", self.n)
        if len(List) == self.n:
            self.n = 0
            print("2:self.found =", self.found, "\nself.n =", self.n)
            return self.found
        if List[self.n] == Object:
            self.found.append(self.n)
            print("3:self.found =", self.found, "\nself.n =", self.n)
            self.n = self.n + 1
            print("4:self.found =", self.found, "\nself.n =", self.n)
            self.search(Object, List)
        else:
            self.n = self.n + 1
            print("5:self.found =", self.found, "\nself.n =", self.n)
            self.search(Object, List)