解决方法

在rolling()方法中添加参数min_periods即可

示例

import pandas as pd
import numpy as np


if __name__ == '__main__':
    data = np.random.randint(0, 10, size=(20))
    series = pd.Series(data)
    series1 = series.rolling(3).mean()
    series2 = series.rolling(3, min_periods=1).mean()
    print(series1) # 前2个数是nan
    print(series2) # 会遇到多少个数，就用多少个数