Get index of DataFrame row-CodePudding

how to get back 10 from df.iloc[10] where df = pd.DataFrame({'a':np.arange(1,12)})? I tried df.index but it returns a weird np.array which doesn't contain anything close to 10.

CodePudding user response：

With df.iloc or df.loc, you obtain a series that corresponds to the columns of a given row in the dataframe:

>>> df
   foo
a   44
b   34
c   65
>>> df.iloc[1]
foo    34
Name: b, dtype: int64
>>> df.index[1]
'b'
>>> df.loc['b']
foo    34
Name: b, dtype: int64

You can see that the index of this second row, here b, is kept as the name of the series. Hence we can use it to find the position in the index:

>>> ser = df.iloc[1]
>>> df.index.get_indexer([ser.name])[0]
1

Note that Index.get_indexer only works with arrays, hence the need to get the first element of the answer.

Alternately you can always convert the index to a list and use list.index to find the element position, but this will likely be much slower:

>>> df.index.to_list().index(ser.name)
1

CodePudding user response：

The most simple solution if the index matches the row numbers is df.iloc[10].name which returns 10