如何提取 DateTimeIndex 以在新列中使用？ (How do I extract a DateTimeIndex for use in a new column?)

問題描述

如何提取 DateTimeIndex 以在新列中使用？ (How do I extract a DateTimeIndex for use in a new column?)

我已從一組 Excel 文件中的文件名中提取日期到 DateTimeIndex 對象列表中。我現在需要將每個提取的日期寫入我從每個 Excel 工作表創建的數據框的新日期列。我的代碼的工作原理是將新的“日期”列寫入每個數據幀，但我無法將對像從它們的生成器對象 DateTimeIndex 格式轉換為 %Y‑%m‑%d 格式。

鏈接到從文件名創建 DateTimeIndexes 列表的代碼：如何將 datefinder 輸出轉換為列表？

將每個列表條目寫入從電子表格創建的每個數據框中的新“日期”列的代碼：

參考解法

方法 1:

1. force evaluation with a one line loop like dates = [_ for _ in matches]
2. convert the index to a column using the .index (or .reset_index() if you don't need to keep it)
3. convert the column to datetime using pd.to_datetime() . use the .dt.date object of the datetime column to convert to Y‑m‑d

</ol>

Here's a sample

import datefinder
import pandas as pd

data = '''Your appointment is on July 14th, 2016 15:24. Your bill is due 05/05/2016 16:00'''
matches = datefinder.find_dates(data)
# force evaluation with 1 line loop
dates = [_ for _ in matches] # 'dates = list(matches)' also works
df = pd.DataFrame({'dt_index':dates,'value':['appointment','bill']}).set_index('dt_index')
df['date'] = df.index
df['date'] = pd.to_datetime(df['date'])
df['date'] = df['date'].dt.date
df

which gives

value   date
dt_index        
2016‑07‑14 15:24:00 appointment 2016‑07‑14
2016‑05‑05 16:00:00 bill    2016‑05‑05

Edit: Edited to account for forced evaluation

方法 2:

A minor fix got it working, I was just trying to carry out too much at once and overthinking it.

#create empty list and append each date 
event_dates_transfer = []
#use .strftime('%Y‑%m‑%d') method on event_dates_dto here if you wish to return a string instead of a datetimeindex
for i in range(0,len(event_dates_dto)):
    event_dates_transfer.append(event_dates_dto[i][0])

#Create a 'Date' column for each dataframe correlating to the filename it was created from and set it as the index
for i in range(0, len(df)):
    new_date = event_dates_transfer[i]
    df[i]['Date'] = new_date
    df[i].set_index('Date', inplace=True)

(by Naeblis、rhedak、Naeblis)

參考文件

1. How do I extract a DateTimeIndex for use in a new column? (CC BY‑SA 2.5/3.0/4.0)