如何在 python 数据框中组合索引？

Question

in the following, can I make a single index for all the entries with common index.

cric = pd.Series(['India', 'Pakistan', 'South Africa', 'England', 'New Zealand'], 
                 index = ['Cricket', 'Cricket', 'Cricket', 'Cricket', 'Cricket'])
ftbl = pd.Series(['England', 'South Africa', 'Australia', 'Netherlands', 'New Zealand'], 
                 index = ['Football', 'Football', 'Football', 'Football' , 'Football'])
hock = pd.Series(['India', 'Pakistan', 'South Korea', 'England', 'India', 'New Zealand'], 
                 index = ['Hockey', 'Hockey', 'Hockey', 'Hockey', 'Hockey', 'Hockey'])

all_countries_1 = cric.append(ftbl)
all_countries_1 = all_countries_1.append(ftbl)
all_countries_1 = all_countries_1.append(hock)
all_countries_1 = all_countries_1.to_frame()
all_countries_1.columns = ['Countries']
all_countries_1

I want the following as my out

Answer 1

If, by single index, you mean an index made of autoincrementing numbers, there is nothing special you have to do. That is the default index for a DataFrame, so using the reset_index() method will get what you want. The next step will probably be to rename your index column. You can chain that method with reset_index and take care of it one line.

all_countries_1 = all_countries_1.reset_index().rename(columns={"index":"Sports"})

Answer 2

Is this what you are looking for?

# zip the first three chars of the index and the index together
z = list(zip(all_countries_1.index.str[:3], all_countries_1.index))
# create multi index
idx = pd.MultiIndex.from_tuples(z)
# assign index
all_countries_1.index = idx

                 Countries
Cri Cricket          India
    Cricket       Pakistan
    Cricket   South Africa
    Cricket        England
    Cricket    New Zealand
Foo Football       England
    Football  South Africa
    Football     Australia
    Football   Netherlands
    Football   New Zealand
    Football       England
    Football  South Africa
    Football     Australia
    Football   Netherlands
    Football   New Zealand
Hoc Hockey           India
    Hockey        Pakistan
    Hockey     South Korea
    Hockey         England
    Hockey           India
    Hockey     New Zealand