生日悖论数量在python中不断增长

Question

我需要这段代码来输出匹配生日的总数，但总数一直在增长，我不知道为什么。我们预计总共会看到大约一半的模拟量。我现在把它附加到一个列表中，以直观地显示计数的变化。

import random
birthmonth = []
birthday= []
def birthday_paradox():
"""

"""
months31 = (1,3,5,7,8,10,12)
months30 = (4,6,9,11)
day31 = random.randint(1,31)
day30 = random.randint(1,30)
day29 = random.randint(1,29)
month = random.randint(1,12)

for i in months31:
if month == i:
birthmonth.append(month)
birthday.append(day31)
for i in months30:
if month == i:
birthmonth.append(month)
birthday.append(day30)
if month == 2:
birthmonth.append(month)
birthday.append(day29)
def frequency_of_matches(number_of_people:int = 23):
"""

"""
count = 0
for i in range(number_of_people):
birthday_paradox()
sorted_birthday_list = sorted(list(zip(birthmonth, birthday))) 

for i in range(len(sorted_birthday_list)):
if sorted_birthday_list[i] == sorted_birthday_list[i - 1]:
count += 1
return count


def simulations(number_of_simulations:int = 100):
total = []
for i in range(number_of_simulations):
total.append(frequency_of_matches())
return total

simulations(25)

示例输出：

[1, 3, 7, 9, 13, 23, 28, 42, 51, 61, 70, 84, 97, 112, 124, 138, 153, 163, 178, 196, 213, 228, 244, 261, 277]

Answer 1

根本问题是birthmonth和birthday列表不断增长。你永远不会清除它们。这就是为什么你的设计——修改全局变量——是一个糟糕的设计。函数应该重新启动并返回其输出。全球化是邪恶的。

此外，你随意选择生日的方法是疯狂的。这里有一个替换，它只需要一个随机数，并且只使用一个全局，这是一个常数。

import random
import datetime
jan1 = datetime.datetime(2022,1,1)
def birthday_paradox():
base = jan1 + datetime.timedelta(days=random.randint(0,364))
return base.month,base.day
def frequency_of_matches(number_of_people:int = 23):
birthdays = [birthday_paradox() for i in range(number_of_people)]
birthdays.sort()

count = 0
for i in range(len(birthdays)-1):
if birthdays[i] == birthdays[i+1]:
count += 1
return count

def simulations(number_of_simulations:int = 100):
total = []
for i in range(number_of_simulations):
total.append(frequency_of_matches())
return total
print(simulations(25))

如果你真的，真的为这里缺少2月29日而烦恼，那么改为：

base = jan1 + datetime.timedelta(days=random.randint(0,365*4+1))