python - Pandas series.apply 出现溢出错误

Question

我有一个函数可以很好地处理单个值，但是当我将它与 pandas series.apply() 一起使用时，它会出现 OverflowError。

from __future__ import division
import pandas as pd
import numpy as np

birthdays = pd.DataFrame(np.empty([365,2]), columns = ['k','probability'], index = range(1,366))
birthdays['k'] = birthdays.index

我做了一个函数:

def probability_of_shared_bday(k):
    end_point = 366 - k
    numerator = 1
    for i in range(end_point, 366):
        numerator = numerator*i
    denominator = 365**k
    probability_of_no_match = (1 - numerator/denominator)
    return probability_of_no_match

当我用单个整数尝试这个时，它工作正常:

 probability_of_shared_bday(1)

0.0

 probability_of_shared_bday(100)

0.9999996927510721

但是当我尝试将此函数与应用一起使用时:

birthdays['probability'] = birthdays['k'].apply(probability_of_shared_bday, convert_dtype=False)

OverflowError:整数除法结果对于 float 来说太大

无论 convert_dtype 是 True 还是 False，都会发生这种情况。

检查 birthdays['k'].dtypes 我得到 dtype('int64')

Answer 1

我不确定为什么 apply 会出现这个问题，但您不应该像最初那样编写函数。这里有一个避免将两个大数相除的建议:

def probability_of_shared_bday(k):
    end_point = 366 - k
    ratio = 1
    for i in range(end_point, 366):
        ratio *= i / 365
    probability_of_no_match = (1 - ratio)
    return probability_of_no_match

问题就迎刃而解了!