使用 pandas.to_csv 时如何指定日期格式？

Question

The default output format of to_csv() is:

12/14/2012  12:00:00 AM

I cannot figure out how to output only the date part with specific format:

20121214

or date and time in two separate columns in the csv file:

20121214,  084530

The documentation is too brief to give me any clue as to how to do these. Can anyone help?

Answer 1

从Pandas 的 v0.13.0（2014 年 1 月 3 日）版本开始，您可以使用to_csv方法的date_format参数：

df.to_csv(filename, date_format='%Y%m%d')

Answer 2

You could use strftime to save these as separate columns:

df['date'] = df['datetime'].apply(lambda x: x.strftime('%d%m%Y'))
df['time'] = df['datetime'].apply(lambda x: x.strftime('%H%M%S'))

and then be specific about which columns to export to csv:

df[['date', 'time', ... ]].to_csv('df.csv')

Answer 3

To export as a timestamp, do this:

df.to_csv(filename, date_format='%s')

The %s format is not documented in python/pandas but works in this case.

I found the %s from the dates formats of ruby . Strftime doc for C here

Note that the timestamp miliseconds format %Q does not work with pandas (you'll have a litteral %Q in the field instead of the date). I caried my sets with python 3.6 and pandas 0.24.1

Answer 4

Non of these timestamp formats seem to work for me.

Tried:

from datetime import datetime
ordersUnleashed.to_csv('sendtoUnleashed.csv', date_format='%s.%f')

And from https://lifewithdata.com/2021/12/10/pandas-to_csv-write-a-dataframe-to-a-csv-file/#specifying-datetime-format-when-saving-a-csv-file

No luck. Even tried pip install datetime.