python实现香农编码

【运行截图】

【核心代码】

from math import *
class Shannon:
    code_dict={}
    code_length_list=[]
    CumulativeProbabilityList=[]
    x_p={}
    x_plist=[]
    AvgCodeLength=0
    CodingEfficiency=0

    def sort(self,data: str):
        # 统计信源中各个概率
        self.x_p = {}  # 一个信源和概率对应的字典
        x_list = []
        for i in data:
            if i not in x_list:
                x_list.append(i)
        length = len(data)
        for i in x_list:
            self.x_p[i] = data.count(i) / length
        # 对概率进行降序排序 并返回一个列表
        self.x_plist = sorted(self.x_p.items(), key=lambda kv: kv[1])  # 直接百度找来的字典跟据值进行排序
        # 返回一个列表 列表元素是一个元组 元组有两个东西组成,分别是字符和概率
        self.x_plist= self.x_plist[::-1]
        return self.x_plist
    def ShannonCoding(self):  # 香农编码
        self.code_length_list = []  # 存放各个码的码长
        for i in self.x_plist:  # 生成码长列表
            self.code_length_list.append(int(1 - (log(i[1], 2))))
        self.CumulativeProbabilityList = []  # 存放累加概率
        # 第一位直接存0
        self.CumulativeProbabilityList.append(0)
        for i in range(1, len(self.x_plist)):
            sum = 0
            for j in range(0, i):
                sum = self.x_plist[j][1]
            self.CumulativeProbabilityList.append(sum)
        self.code_dict = {}  # 码字列表
        for i in range(0, len(self.CumulativeProbabilityList)):
            self.code_dict[self.x_plist[i][0]] = self.float2bin(self.CumulativeProbabilityList[i], self.code_length_list[i])

#计算平均码长
        avg = 0
        for i in range(0, len(self.code_length_list)):
            avg = self.code_length_list[i] * self.x_plist[i][1]
        self.AvgCodeLength=avg
        #计算编码效率
        Hx = 0
        for i in range(0,len(self.code_length_list)):
            Hx =-(self.x_plist[i][1]*log(self.x_plist[i][1],2))
        self.CodingEfficiency=Hx/self.AvgCodeLength
        return self.code_dict

    # 计算小数二进制
    def  float2bin(self,float, len=10):
        res = ''
        for i in range(0, len):
            float = float * 2
            if float >= 1:
                res = '1'
                float -= 1
            else:
                res = '0'
        return res