python - How do I round datetime column to nearest quarter hour

Question

I have loaded a data file into a Python pandas dataframe. I has a datetime column of the format 2015-07-18 13:53:33.280.

What I need to do is create a new column that rounds this out to its nearest quarter hour. So, the date above will be rounded to 2015-07-18 13:45:00.000.

How do I do this in pandas? I tried using the solution from here, but get an 'Series' object has no attribute 'year' error.

Answer 1

You can use round(freq). There is also a shortcut column.dt for datetime functions access (as @laurens-koppenol suggests).

Here's one-liner:

df['old column'].dt.round('15min')  

String aliases for valid frequencies can be found here. Full working example:

In [1]: import pandas as pd    
In [2]: df = pd.DataFrame([pd.Timestamp('2015-07-18 13:53:33.280'),
                           pd.Timestamp('2015-07-18 13:33:33.330')],
                         columns=['old column'])

In [3]: df['new column']=df['old column'].dt.round('15min')  
In [4]: df
Out[4]: 
               old column          new column
0 2015-07-18 13:53:33.280 2015-07-18 14:00:00
1 2015-07-18 13:33:33.330 2015-07-18 13:30:00