How to find index in a string format for a particular value in a column of a pandas dataframe?

Question

I have a dataframe named Top15 like this:  
Country              % Renewable Energy   Rank
Brazil               69.65                15
Canada               61.95                56
China                19.75                32
Germany              17.90                 2
Spain                37.97                11
France               17.02                12
United Kingdom       10.60                 5
India                14.97                10
Iran                  5.71                21
......                ......             .....

United States        11.57                38

Here i want to find the Country with greatest %Renewable Energy. 
Here country is the index of dataframe and hence i want the name of index only in string format.
But when i use the following code:
maximum=Top15['% Renewable'].max()
Top15[Top15['% Renewable']==maximum].index       (Method 1)
I get :Index(['Brazil'], dtype='object', name='Country')  

But when i use: Top15[Top15['% Renewable']==maximum].index[0] (Method 2)
I get:'Brazil'

So i am unable to understand that what is the meaning of index[0] here and how it is giving only the index in a string format(which i want as output) compared to method 1. Also when i am using index[1] i am getting error: IndexError: index 1 is out of bounds for axis 0 with size 1

Can somebody please clarify the meaning of index[0] here?

Answer 1

When you are calling .index it returns you the index object, the only element of which, 'Brazil' , is accessible via indexing the index object at position 0, so .index[0] .

When you are calling .index[1] you are trying to access the second element of the index object while it only contains one element, hence the error.