Group sorting longitudinal (panel) data depending on data and asset

Question

I've been trying to sort my panel data (pandas DF) which is divided into several assets and different starting dates per each. The idea is to discover which starts the earliest, so that it can be placed in the beginning, and when it ends, the second earliest is stacked right after that.

See the data below (current situation):

Date (index)	Feature	Asset_id
01/01/1999	feature_asset_1	Asset_1
02/01/1999	feature_asset_1	Asset_1
03/01/1999	feature_asset_1	Asset_1
04/01/1999	feature_asset_1	Asset_1

...

Date (cont'd)	Feature (cont'd)	Asset_id (cont'd)
01/01/2020	feature_asset_1	Asset_1
02/01/2020	feature_asset_1	Asset_1
03/01/2020	feature_asset_1	Asset_1
01/01/1998	feature_asset_2	Asset_2
02/01/1998	feature_asset_2	Asset_2
03/01/1998	feature_asset_2	Asset_2

And the idea is to basically move Asset_2 to the beginning (since it starts earlier), like this:

Date (index)	Feature	Asset_id
01/01/1998	feature_asset_2	Asset_2
02/01/1998	feature_asset_2	Asset_2
03/01/1998	feature_asset_2	Asset_2
04/01/1999	feature_asset_2	Asset_2

...

Date (cont'd)	Feature (cont'd)	Asset_id (cont'd)
01/01/2020	feature_asset_2	Asset_2
02/01/2020	feature_asset_2	Asset_2
03/01/2020	feature_asset_2	Asset_2
01/01/1999	feature_asset_1	Asset_1
02/01/1999	feature_asset_1	Asset_1
03/01/1999	feature_asset_1	Asset_1

There are about 10 different assets, each begin on a different date. How do I make the sort, per date and asset id, so that it also takes into consideration the starting date of each asset? Sort_values by "Date" and "Asset_id", does not work because it will sort alphabetically.

Answer 1

You need to convert the column "Date" to datetime type before sorting it:

df['Date'] = pd.to_datetime(df['Date'])
df = df.sort_values(by=['Date','Asset_id'])
df

Result:

index	Date	Feature	Asset_id
2	1998-01-01 00:00:00	feature_asset_2	Asset_1
0	1999-01-01 00:00:00	feature_asset_1	Asset_1
1	2000-01-01 00:00:00	feature_asset_1	Asset_1
5	2001-01-01 00:00:00	feature_asset_2	Asset_1
3	2001-01-01 00:00:00	feature_asset_1	Asset_2
4	2001-01-01 00:00:00	feature_asset_1	Asset_3