将导入的日期从.txt转换为日期格式python

我在导入的.txt文件中转换日期时遇到问题，我想知道我做错了什么。

我通过以下方式导入数据：

df_TradingMonthlyDates = pd.read_csv(TradingMonthlyDates, dtype=str, sep=',') # header=True,

看起来像下表（日期代表月份的开始/结束并有标头Date）：

           Date
0    2008-12-30
1    2008-12-31
2    2009-01-01
3    2009-01-02
4    2009-01-29
..          ...

557  2020-06-29
558  2020-06-30
559  2020-07-01
560  2020-07-02
561  2020-07-30
..          ...

624  2021-11-30
625  2021-12-01
626  2021-12-02
627  2021-12-30
628  2021-12-31

[629 rows x 1 columns]
<class 'pandas.core.frame.DataFrame'>

然后，我计算今天的日期：

df_EndDate = datetime.now().date()

我试图在此函数中应用上述数据，以获取给定日期之前的最接近日期（在我的情况下，给定日期=今天的日期）：

# https://stackoverflow.com/questions/32237862/find-the-closest-date-to-a-given-date
def nearest(items, pivot):
    return min([i for i in items if i < pivot], key=lambda x: abs(x - pivot))

date_output = nearest(df_TradingMonthlyDates, df_EndDate)
# date_output should be = 2020-07-02 given today's date of 2020-07-12

我收到的错误消息是，df_TradingMonthlyDates它不是日期格式。因此，我试图将数据框转换为日期时间格式，但无法使其正常工作。

我试图将数据转换为日期格式的内容：

# df_TradingMonthlyDates["Date"] = pd.to_datetime(df_TradingMonthlyDates["Date"], format="%Y-%m-%d")
# df_TradingMonthlyDates = datetime.strptime(df_TradingMonthlyDates, "%Y-%m-%d").date()
# df_TradingMonthlyDates['Date'] = df_TradingMonthlyDates['Date'].apply(lambda x: pd.to_datetime(x[0], format="%Y-%m-%d"))
# df_TradingMonthlyDates = df_TradingMonthlyDates.iloc[1:]
# print(df_TradingMonthlyDates)
# df_TradingMonthlyDates = datetime.strptime(str(df_TradingMonthlyDates), "%Y-%m-%d").date()
# for line in split_source[1:]: # skip the first line

码：

import pandas as pd
from datetime import datetime
 
# Version 1

TradingMonthlyDates = "G:/MonthlyDates.txt"

# Import file where all the first/end month date exists
df_TradingMonthlyDates = pd.read_csv(TradingMonthlyDates, dtype=str, sep=',') # header=True,
print(df_TradingMonthlyDates)

# https://community.dataquest.io/t/datetime-and-conversion/213425
# df_TradingMonthlyDates["Date"] = pd.to_datetime(df_TradingMonthlyDates["Date"], format="%Y-%m-%d")
# df_TradingMonthlyDates = datetime.strptime(df_TradingMonthlyDates, "%Y-%m-%d").date()
# df_TradingMonthlyDates['Date'] = df_TradingMonthlyDates['Date'].apply(lambda x: pd.to_datetime(x[0], format="%Y-%m-%d"))
# df_TradingMonthlyDates = df_TradingMonthlyDates.iloc[1:]
# print(df_TradingMonthlyDates)
# df_TradingMonthlyDates = datetime.strptime(str(df_TradingMonthlyDates), "%Y-%m-%d").date()
# for line in split_source[1:]: # skip the first line # maybe header is the problem
print(type(df_TradingMonthlyDates))
df_TradingMonthlyDates = df_TradingMonthlyDates.datetime.strptime(df_TradingMonthlyDates, "%Y-%m-%d")
df_TradingMonthlyDates = df_TradingMonthlyDates.time()


print(df_TradingMonthlyDates)

df_EndDate = datetime.now().date()
print(type(df_EndDate))



# https://stackoverflow.com/questions/32237862/find-the-closest-date-to-a-given-date
def nearest(items, pivot):
    return min([i for i in items if i < pivot], key=lambda x: abs(x - pivot))

date_output = nearest(df_TradingMonthlyDates, df_EndDate)

错误消息会有所不同，具体取决于我尝试转换数据类型的方式，但是我认为它们都注意到我的日期格式不成功：

df_TradingMonthlyDates = df_TradingMonthlyDates.datetime.strptime(df_TradingMonthlyDates, "%Y-%m-%d")

Traceback (most recent call last):
  File "g:/till2.py", line 25, in <module>
    df_TradingMonthlyDates = df_TradingMonthlyDates.datetime.strptime(df_TradingMonthlyDates, "%Y-%m-%d")
  File "C:\Users\ID\AppData\Roaming\Python\Python38\site-packages\pandas\core\generic.py", line 5274, in __getattr__
    return object.__getattribute__(self, name)
AttributeError: 'DataFrame' object has no attribute 'datetime'

df_TradingMonthlyDates["Date"] = pd.to_datetime(df_TradingMonthlyDates["Date"], format="%Y-%m-%d")

Traceback (most recent call last):
  File "g:/till2.py", line 40, in <module>
    date_output = nearest(df_TradingMonthlyDates, df_EndDate)
  File "g:/till2.py", line 38, in nearest
    return min([i for i in items if i < pivot], key=lambda x: abs(x - pivot))
  File "g:/till2.py", line 38, in <listcomp>
    return min([i for i in items if i < pivot], key=lambda x: abs(x - pivot))
TypeError: '<' not supported between instances of 'str' and 'datetime.date'