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,
它看起来像下表（日期代表月份的开始/结束并有一个标题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()
我正在尝试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df_TradingMonthlyDates是不是日期格式。因此，我尝试将数据框转换为日期时间格式，但无法使其正常工作。
我尝试将数据转换为日期格式：
# 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
代码：
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)
错误消息因我尝试转换数据类型的方式而异，但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'