我不知道这方面有什么标准的库工具，但很容易制作自己的，比如：

from datetime import datetime, timedelta
import pandas as pd

test_arr = ['December2009', 'August2012', 'March2015']

def replacer(d):
    # take a datestring of format %B%Y and find the second wednesday 
    dt = datetime.strptime(d, '%B%Y')
    x = 0
    # start at day 1 and increment through until conditions satisfied
    while True:
        s = dt.strftime('%A')
        if s == 'Wednesday':
            x += 1 # if a wednesday found, increment the counter
        if x == 2:
            break # when two wednesdays found then break
        dt += timedelta(days = 1)
    return dt.strftime('%m/%d/%Y')

df = pd.DataFrame(test_arr, columns = ['a'])
df['a'].apply(replacer) # .apply() applies the given python function to each element in the df column

也许其他注解中推荐的日历模块可以使代码看起来更好，但我不熟悉它，因此您可能希望研究改进解决方案