Python根据数值大小随机返回一个key，并保证返回这个key的概率和它所对应的value成正比

题目：def randomSymbol(symbolAndWeight):
”’
Input: symbolAndWeight is a dict of { str: int },
for example, {
‘a’: 2,
‘b’: 3,
‘c’: 5,
}

Returns:
随机返回symbolAndWeight中的一个key，并保证返回这个key的概率和它所对应的value成正比

解答：

#coding:utf-8import randomclass t():    def __init__(self):        pass    def loadData(self):        testData = {'a': '2', 'b': '3', 'c': '5'}        return testData    def randomSymbolol_1(self):        testData = self.loadData()        new_data = {v: k for k, v in testData.items()}        keys = new_data.keys()        list = []        for key in keys:            for i in range(int(key)):                list.append(new_data[key])        index = random.randint(0,len(list)-1)        return list[index]    def randomSymbolol_2(self):        testData = self.loadData()        new_data = {v: k for k, v in testData.items()}        keys = new_data.keys()        keySum = 0        for key in keys:            keySum += int(key)        ran = random.randint(0, keySum-1)        sumtmp = 0        N = len(keys)        for i in range(N):            sumtmp += int(keys[i])            if sumtmp > ran:                a = i                return a        return -1t = t()i = 0a_total1 = 0b_total1 = 0c_total1 = 0while i < 10000:    temp =  t.randomSymbolol_2()    if temp == 1:        a_total1 += 1    elif temp == 0:        b_total1 += 1    else:        c_total1 += 1    i += 1print "result of method 1:"print "a:", a_total1/float(10000)print "b:", b_total1/float(10000)print "c:", c_total1/float(10000)a_total2 = 0b_total2 = 0c_total2 = 0j = 0while j < 10000:    temp = t.randomSymbolol_1()    if temp == 'a':        a_total2 += 1    elif temp == 'b':        b_total2 += 1    else:        c_total2 += 1    j += 1print "result of method 2:"print "a:", a_total2/float(10000)print "b:", b_total2/float(10000)print "c:", c_total2/float(10000)

参考链接：http://blog.sciencenet.cn/home.php?mod=space&uid=404069&do=blog&id=335920