Add column with number of days between dates in DataFrame pandas
I want to subtract dates in 'A' from dates in 'B' and add a new column with the difference.
df A B one 2014-01-01 2014-02-28 two 2014-02-03 2014-03-01
I've tried the following, but get an error when I try to include this in a for loop...
import datetime date1=df['A'] date2=df['B'] mdate1 = datetime.datetime.strptime(date1, "%Y-%m-%d").date() rdate1 = datetime.datetime.strptime(date2, "%Y-%m-%d").date() delta = (mdate1 - rdate1).days print delta
What should I do?
Assuming these were datetime columns (if they're not apply
to_datetime) you can just subtract them:
df['A'] = pd.to_datetime(df['A']) df['B'] = pd.to_datetime(df['B']) In : df.dtypes # if already datetime64 you don't need to use to_datetime Out: A datetime64[ns] B datetime64[ns] dtype: object In : df['A'] - df['B'] Out: one -58 days two -26 days dtype: timedelta64[ns] In : df['C'] = df['A'] - df['B'] In : df Out: A B C one 2014-01-01 2014-02-28 -58 days two 2014-02-03 2014-03-01 -26 days
Note: ensure you're using a new of pandas (e.g. 0.13.1), this may not work in older versions.
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