问题
I am struggling with datetime64 comparisons in dataframes to update a column. lets say we have a dataframe 'df' with a 'date' column
df.date.values[0]
Out[128]: numpy.datetime64('2015-05-17T22:00:00.000000000+0800')
i needed to drop the time and just do a date comparison, so to extract the date i use .date()
df.date[0].date()
Out[131]: datetime.date(2015, 5, 17)
I test it out first
df.date[0].date()==np.datetime64('2015-05-17')
Out[132]: True
So all seems good i try to do a condition if date column equal to a specific date, update another column into another value
df[df.date[0].date()==np.datetime64('2015-05-17')].flag=True
I get a KeyError: True
how do i properly do this?
回答1:
Have you tried something like:
flag = pd.Series(np.where(df.date == np.datetime64('2015-05-17'), True, False), index=df.index)
flag will be a series of True/False values which you use later.
来源:https://stackoverflow.com/questions/30689445/datetime64-comparison-in-dataframes