将 DataFrame 列从字符串转换为日期时间格式“2001 年 1 月 1 日星期一”

Question

I am trying to convert a dataframe column " date " from string to datetime . I have this format: " January 1, 2001 Monday ".

I tried to use the following:

from dateutil import parser
for index,v in df['date'].items():
   df['date'][index] = parser.parse(df['date'][index])  

But it gives me the following error:

ValueError: Cannot set non-string value '2001-01-01 00:00:00' into a StringArray.

I checked the datatype of the column " date " and it tells me string type.

This is the snippet of the dataframe:

Any help would be most appreciated!

Answer 1

You need to specify the format for the datetime object in order it to be parsed correctly. The documentation helps with this:

• %A is for Weekday as locale's full name, eg, Monday
• %B is for Month as locale's full name, eg, January
• %d is for Day of the month as a zero-padded decimal number.
• %Y is for Year with century as a decimal number, eg, 2021.

Combining all of them we have the following function:

from datetime import datetime

def mdy_to_ymd(d):
    return datetime.strptime(d, '%B %d, %Y %A').strftime('%Y-%m-%d')
    
print(mdy_to_ymd('January 1, 2021 Monday'))


> 2021-01-01

One more thing is for your case, .apply() will work faster, thus the code is:

df['date'] = df['date'].apply(lambda x: mdy_to_ymd)

Feel free to add Hour-Minute-Second if needed.

Answer 2

why don't you try this instead of dateutils , pandas offer much simpler tools such as pd.to_datetime function:

df['date'] = pd.to_datetime(df['date'], format='%B %d, %Y %A')