Python : Update Values of a Column based on Date Range from another Data Frame

Question

There are 2 dataframes df and events which look like below:

import pandas as pd

df = pd.DataFrame({'Place':['university','residential','hospital','university','residential','hospital'],
                   'Date':['2017-01-01','2017-01-01','2017-01-01','2017-01-02','2017-01-02','2017-01-02'],
                   'Event':['None','None','None','None','None','None']
                })
events = pd.DataFrame({'Place':['university','residential','hospital'], 'Start_Date':['2017-01-01','2017-01-01','2017-01-01'],
                                      'End_Date':['2017-02-26','2017-01-02','2017-01-02'],
                                       'Event':['UniHolidays','PublicHoliday','PublicHoliday']})

#Convert to datetime
events.Start_Date = pd.to_datetime(events.Start_Date.astype(str), format='%Y-%m-%d')
events.End_Date = pd.to_datetime(events.End_Date.astype(str), format='%Y-%m-%d')
df.Date = pd.to_datetime(df.Date.astype(str), format='%Y-%m-%d')

df has 1 record for every date in 2017 for each place

df:
    Date         Place            Event
    2017-01-01   university        None
    2017-01-01   residential       None
    2017-01-01   hospital          None
    2017-01-02   university        None
    2017-01-02   residential       None
    2017-01-02   hospital          None

The second dataframe contains events for these places but with a date range

events:

Place     Start_Date     End_Date   Event
a      2017-01-01      2017-02-26   UniHoliday
b      2017-01-01      2017-01-02   PublicHoliday
c      2017-01-01      2017-01-02   PublicHoliday

The task is to update df using events such that

if df.Place = events.Place and df.Date is in range ( events.Start_Date, events.End_Date ) then df.Event should be updated with the corresponding event.Event

The expected output is:

Date        Place                Event
    2017-01-01  university       UniHoliday
    2017-01-01  residential      PublicHoliday
    2017-01-01  hospital         PublicHoliday
    2017-01-02  university       UniHoliday
    2017-01-02  residential      PublicHoliday
    2017-01-02  hospital         PublicHoliday

There are no overlapping events, every place has a unique record of events

so far I have been thinking along the lines of: Populate column in data frame based on a range found in another dataframe ,But can't get my head around it. Any help is appreciated. Thank you!

Answer 1

Solution 1:

Add:

df['Event']=events['Event'].tolist()*2

To the end of the code.

Then now:

print(df)

Is:

        Date          Event        Place
0 2017-01-01    UniHolidays   university
1 2017-01-01  PublicHoliday  residential
2 2017-01-01  PublicHoliday     hospital
3 2017-01-02    UniHolidays   university
4 2017-01-02  PublicHoliday  residential
5 2017-01-02  PublicHoliday     hospital

----------------------------------------

Solution 2:

If want them to add in the right place do:

df=df.drop('Event',1)
df.insert(2,'Event',events['Event'].tolist()*2)

In the end of the code.

Then now:

print(df)

Outputs:

        Date        Place          Event
0 2017-01-01   university    UniHolidays
1 2017-01-01  residential  PublicHoliday
2 2017-01-01     hospital  PublicHoliday
3 2017-01-02   university    UniHolidays
4 2017-01-02  residential  PublicHoliday
5 2017-01-02     hospital  PublicHoliday

---------------------------------------------------------------

Solution 1 + Solution 2 , will work,

But still best is to do singularly.

Update:

Use:

df=df.drop('Event',1)
df.insert(2,'Event',events['Event'].tolist()*(len(df['Event'])/len(events['Event'].tolist())))

In the end of the code.

Then now:

print(df)

Outputs:

        Date        Place          Event
0 2017-01-01   university    UniHolidays
1 2017-01-01  residential  PublicHoliday
2 2017-01-01     hospital  PublicHoliday
3 2017-01-02   university    UniHolidays
4 2017-01-02  residential  PublicHoliday
5 2017-01-02     hospital  PublicHoliday