find middle node in singly linked list

find_middle.py

#!/usr/bin/env python
# encoding: utf-8


class Node(object):

    def __init__(self, value, next=None):

        self.value = value
        self.next = next


def find_middle(node):

    slow = fast = node

    while fast:

        fast = fast.next

        if fast:
            fast = fast.next
            slow = slow.next

    return slow


def gen_link(num):

    node = None

    for i in range(num):
        node = Node(i, node)

    return node

n = gen_link(11)

m = find_middle(n)

print n.value, m.value