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1. ???????

??????????????????????????????Python???????????????????????Python???????????????????????????????????????????

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2. Python???????

?Python?????????????????????????????????

a = 10
b = 20

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a, b = b, a

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a, b = 20, 10

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3. Python?????

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class Node(object):
    """???"""
    def __init__(self, elem):
        self.elem = elem
        self.next = None

???????????

• is_empty()??????????
• length()????????
• travel()??????
• add(item)?????????
• append(item)?????????
• insert(pos, item)???????????
• remove(item)????????
• search(item)??????????

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class SingleLinkList(object):
    """????"""
    def __init__(self, node=None):
        self.__head = node  # ????
    def is_empty(self):
        """????????"""
        return self.__head is None
    def length(self):
        """??????"""
        count = 0
        cur = self.__head
        while cur is not None:
            count += 1
            cur = cur.next
        return count
    def travel(self):
        """???????????"""
        cur = self.__head
        while cur is not None:
            print(cur.elem, end=" ")
            cur = cur.next
        print()
    def add(self, item):
        """??????????"""
        node = Node(item)
        node.next = self.__head
        self.__head = node
    def append(self, item):
        """??????????"""
        node = Node(item)
        if self.is_empty():
            self.__head = node
        else:
            cur = self.__head
            while cur.next is not None:
                cur = cur.next
            cur.next = node
    def insert(self, pos, item):
        """??????????"""
        if pos <= 0:
            self.add(item)
        elif pos >= self.length():
            self.append(item)
        else:
            pre = self.__head
            count = 0
            while count < pos - 1:
                pre = pre.next
                count += 1
            node = Node(item)
            node.next = pre.next
            pre.next = node
    def remove(self, item):
        """??????"""
        cur = self.__head
        pre = None
        while cur is not None:
            if cur.elem == item:
                if pre is None:
                    self.__head = cur.next
                else:
                    pre.next = cur.next
                break
            pre = cur
            cur = cur.next
    def search(self, item):
        """????????"""
        cur = self.__head
        while cur is not None:
            if cur.elem == item:
                return True
            cur = cur.next
        return False

4. ??????

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5. ????????

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