Groupby first two earliest dates, then average time between first two dates - pandas

Question

I\'m hoping to groupby users and find the first two uploads. I\'ve figured out how to get the first date via minimum, but I\'m having trouble getting that second upload date. Th

Answer 1

Since the other answers explain pretty well how to achieve this, I'll give you a one-liner for a change

 In [1]: df.groupby('User_ID').apply(lambda g: g.sort_values('Date_Uploaded')['Date_Uploaded'][:2].diff()).mean()
 Out[1]: Timedelta('21 days 12:00:00')

Answer 2

sort, calculate the difference and then groupby + nth(1) to get the difference between the first uploads, if it exists (users with 1 date will not show up).

import pandas as pd

df['Date_Uploaded'] = pd.to_datetime(df.Date_Uploaded)
df = df.sort_values(['User_ID', 'Date_Uploaded'])

df.Date_Uploaded.diff().groupby(df.User_ID).nth(1)

#User_ID
#abc123   36 days
#efg123    7 days
#Name: Date_Uploaded, dtype: timedelta64[ns]

---

If you just want the average then average that series:

df.Date_Uploaded.diff().groupby(df.User_ID).nth(1).mean()
#Timedelta('21 days 12:00:00')

Answer 3

Using sort_values + head

df.sort_values('Date_Uploaded').groupby('User_ID').head(2)
Out[152]: 
  Date_Uploaded User_ID Display_Status
6    2018-07-25  efg123        Pending
5    2018-08-01  efg123        Pending
3    2018-09-21  abc123        Pending
0    2018-10-27  abc123        Cleared