这个声明在python中是什么意思?

Question

节点的定义。

class Node:
def __init__(self, x: int, next: 'Node' = None, random: 'Node' = None):
self.val = int(x)
self.next = next
self.random = random
def copyRandomList(self, head: 'Optional[Node]') -> 'Optional[Node]':

为什么next和random初始化为'Node' = None in definit？为什么可选的[Node]在函数声明中包含在" copyRandomList

，而ListNode:

则不同

class ListNode:
def __init__(self, val=0, next=None):
self.val = val
self.next = next
class Solution:
def reorderList(self, head: Optional[ListNode]) -> None:

Answer 1

当类型提示包含尚未定义的名称时，该定义可以表示为字符串字面值，稍后再解析。请阅读以下内容:https://peps.python.org/pep-0484/#forward-references