哈夫曼编码+python实现
关于哈夫曼树怎么构建的、哈夫曼编码怎么求,请参考
哈夫曼树及python实现
这些基础的东西就不在这里阐述了,本文直接上代码。
参考链接:哈夫曼树的 Python 实现
哈夫曼树的构建和编码
'''
huffman编码
'''
import copy
class Node:
def __init__(self, name, weight):
self.name = name #节点名
self.weight = weight #节点权重
self.left = None #节点左孩子
self.right = None #节点右孩子
self.father = None # 节点父节点
#判断是否是左孩子
def is_left_child(self):
return self.father.left == self
#创建最初的叶子节点
def create_prim_nodes(data_set, labels):
if(len(data_set) != len(labels)):
raise Exception('数据和标签不匹配!')
nodes = []
for i in range(len(labels)):
nodes.append( Node(labels[i],data_set[i]) )
return nodes
# 创建huffman树
def create_HF_tree(nodes):
#此处注意,copy()属于浅拷贝,只拷贝最外层元素,内层嵌套元素则通过引用,而不是独立分配内存
tree_nodes = nodes.copy()
while len(tree_nodes) > 1: #只剩根节点时,退出循环
tree_nodes.sort(key=lambda node: node.weight)#升序排列
new_left = tree_nodes.pop(0)
new_right = tree_nodes.pop(0)
new_node = Node(None, (new_left.weight + new_right.weight))
new_node.left = new_left
new_node.right = new_right
new_left.father = new_right.father = new_node
tree_nodes.append(new_node)
tree_nodes[0].father = None #根节点父亲为None
return tree_nodes[0] #返回根节点
#获取huffman编码
def get_huffman_code(root, nodes):
codes = {}
for node in nodes:
code=''
name = node.name
while node.father != None:
if node.is_left_child():
code = '0' + code
else:
code = '1' + code
node = node.father
codes[name] = code
return codes
if __name__ == '__main__':
labels = ['a','b','c','d','e','f']
data_set = [9,12,6,3,5,15]
nodes = create_prim_nodes(data_set,labels)#创建初始叶子节点
root = create_HF_tree(nodes)#创建huffman树
codes = get_huffman_code(root, nodes)#获取huffman编码
#打印huffman码
for key in codes.keys():
print(key,': ',codes[key])
运行结果如下:
a : 00
b : 01
c : 100
d : 1010
e : 1011
f : 11