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-8
import random

class 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 -1

t = t()
i = 0
a_total1 = 0
b_total1 = 0
c_total1 = 0
while i < 10000:
temp =  t.randomSymbolol_2()
if temp == 1:
a_total1 += 1
elif temp == 0:
b_total1 += 1
else:
c_total1 += 1
i += 1
print "result of method 1:"
print "a:", a_total1/float(10000)
print "b:", b_total1/float(10000)
print "c:", c_total1/float(10000)

a_total2 = 0
b_total2 = 0
c_total2 = 0
j = 0
while j < 10000:
temp = t.randomSymbolol_1()
if temp == 'a':
a_total2 += 1
elif temp == 'b':
b_total2 += 1
else:
c_total2 += 1
j += 1
print "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