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pythonpandaspython-datetime

Compare only time in datetime to string in form HH:MM:SS

I have a column in pandas df with string datetime like below

a,dtime
1,2017-07-06 09:15:00
1,2017-07-06 10:15:00

I am writing a script that needs to compare time

I need to compare like df[df.dtime < "10:15:00"] (without date) So I converted df['dtime']=pd.to_datetime(df['dtime']) If I do

df[df.dtime < "10:15:00"]

it takes today date as default and would always compare with today's "10:15:00" what I don't want.

So I created another column and then did it like below 

df['ts']=df.dtime.apply(lambda x: x.time())
df[df.ts<"09:16:00"]
TypeError: can't compare datetime.time to str
df[df.ts<pd.to_datetime("09:16:00").time()] #this works well

Is there a better way to do this simple task, I dont see any point creating a new ts column.

When I do df['dtime']=pd.to_datetime(df['dtime']) I should only extract time part. But doing df['dtime']=pd.to_datetime(df['dtime']).time() gives error AttributeError: 'Series' object has no attribute 'time'

Solution

  • You need to use time or timedelta instead of datetime. You can access it vie the .dt. methods

    t = pd.to_datetime('10:15:00').time()

    df['dtime'].dt.time < t

    0    True
1    False
Name: dtime, dtype: bool