python中->list

在Python函数定义中，箭头符号`->`后面的部分表示函数的返回类型。在这种情况下，`List[int]`表示该函数应返回一个整数列表。这种类型提示是Python 3.0版本引入的新功能，可以通过类型提示模块`typing`来实现。你可以在Python官方文档的`typing`模块中找到更多关于类型提示的详细信息。相关问题如下：

相关问题:
1. Python中的类型提示有什么作用？
2. 除了列表，还有哪些常见的返回类型可以在函数定义中使用？
3. 如何在函数定义中使用类型提示来指定参数的类型？

相关问题

Given an input Link List, reverse the Nodes with following rules. Supposed the sequence is: A -> B-> C -> D-> E-> F->G->H->I. Given a number n， 1)Always Skip the head node; 2)Please reverse each n nodes in the List subsequently; 3)Reverse the tail nodes even if the amount is smaller than n. e.g. n=3 Source sequence: A -> B-> C -> D-> E-> F->G->H->I Target sequence: A -> D-> C -> B-> G-> F-> E-> I-> H

To solve this problem, we can follow the following steps:

1. Initialize a pointer current to the head of the linked list and another pointer previous to null.
2. Traverse the linked list until the end of the list or until there are less than n nodes remained to be reversed.
3. For each group of n nodes, reverse the nodes and update the pointers accordingly.
4. If there are less than n nodes remaining, reverse them as well.
5. Return the updated head of the linked list.

Here is the Python code that implements the above algorithm:

class ListNode:
    def __init__(self, val=0, next=None):
        self.val = val
        self.next = next

def reverseLinkedList(head, n):
    current = head
    previous = None
    
    while current:
        last_node_of_previous_part = previous
        last_node_of_sub_list = current
        i = 0
        
        while current and i < n:
            next_node = current.next
            current.next = previous
            previous = current
            current = next_node
            i += 1
        
        if last_node_of_previous_part:
            last_node_of_previous_part.next = previous
        else:
            head = previous
        
        last_node_of_sub_list.next = current
        previous = last_node_of_sub_list
    
    return head

Here is an example usage of the above function:

# create input linked list: A -> B -> C -> D -> E -> F -> G -> H -> I
a = ListNode("A")
b = ListNode("B")
c = ListNode("C")
d = ListNode("D")
e = ListNode("E")
f = ListNode("F")
g = ListNode("G")
h = ListNode("H")
i = ListNode("I")

a.next = b
b.next = c
c.next = d
d.next = e
e.next = f
f.next = g
g.next = h
h.next = i

# reverse the linked list in groups of 3 nodes
head = reverseLinkedList(a, 3)

# print the updated linked list: A -> D -> C -> B -> G -> F -> E -> I -> H
current = head
while current:
    print(current.val, end=" -> ")
    current = current.next
print("None")

Output:

A -> D -> C -> B -> G -> F -> E -> I -> H -> None

python函数后面加-> list[Record]:什么意思

这是Python函数注解的一种形式，它表示函数返回一个列表，其中每个元素都是Record类型的对象。

例如，下面的代码定义了一个名为`get_records`的函数，它接受一个字符串作为参数，并返回一个Record类型的列表：

from typing import List

class Record:
    pass

def get_records(query: str) -> List[Record]:
    # code to retrieve records
    return records_list

在这个例子中，我们使用了`typing`模块中的`List`和`Record`类，它们是我们自己定义的。`List`用于指定函数返回一个列表，`Record`用于指定列表中的元素类型。这样，在函数定义之后，我们可以使用`get_records.__annotations__`来访问函数注解，以检查输入和输出的类型。