在帶有“季節”（季節1，季節2 ...）列的熊貓DF中，需要將6個月或~182天添加到不為空的最后一個季節

Question

我有一個有多個季節的熊貓 DF，對於每一行，我需要將 6 個月（~182 天）添加到不為空的上一季。日期是 dtype dtype: datetime64[ns] 。

df ：

    S1          S2             S3
2020-12-31      naT            naT
2020-12-31      naT            naT
2020-12-31    2020-12-31       naT
2020-12-31    2020-12-31    2021-01-31

期望輸出：

   S1            S2             S3
2021-06-30      naT            naT
2021-06-30      naT            naT
2020-12-31    2021-06-30       naT
2020-12-31    2020-12-31    2021-07-31

Answer 1

使用.shift()查找行中的下一個單元格是否為 NaT，然后使用pd.DateOffset()為這些單元格添加額外的月份：

import pandas as pd
from io import StringIO

text = """
S1            S2             S3
2020-12-31    naT            naT
2020-12-31    naT            naT
2020-12-31    2020-12-31     naT
2020-12-31    2020-12-31     2021-01-31
"""

df = pd.read_csv(StringIO(text), header=0, sep='\s+')
df = df.apply(pd.to_datetime, errors='coerce')

# find in which cells the next value is na
next_value_in_row_na = df.shift(-1, axis=1).isna()

# for each cell where the next value is na, try to add 6 months
df = df.mask(next_value_in_row_na, df + pd.DateOffset(months=6))

結果數據框：

    S1          S2          S3
0   2021-06-30  NaT         NaT
1   2021-06-30  NaT         NaT
2   2020-12-31  2021-06-30  NaT
3   2020-12-31  2020-12-31  2021-07-31