Sort a pandas Series by the index

Question

I have a Pandas dataframe called pd, and I extract the number of unique values in one of the columns of this dataframe using the following command:

b = df.groupby('Region').size()

b is a Pandas series object and looks like this:

In [48]: b
Out[48]: 
Region
0          8
1         25
11         1
2         41
3         23
4         15
5         35
6         24
7         27
8         50
9         55
N         10

I am trying to plot a barchart of this series, however, I would like to sort it first based on the first column (because of that 11 between 1 and 2), which will be the x axis labels. I tried passing the sort command, but it sorts the series based on the values in the second column:

b.sort()

In [48]: b
Out[54]: 
Region
11         1
0          8
N         10
4         15
3         23
6         24
1         25
7         27
5         35
2         41
8         50
9         55

Well, is there a way to sort this series based on the first column?

Answer 1

You are looking for sort_index:

In [80]: b.sort_values()
Out[80]: 
6     1
11    2
9     2
1     4
10    4
2     5
3     6
4     7
8     8
5     9
dtype: int64

In [81]: b.sort_index()
Out[81]: 
1     4
2     5
3     6
4     7
5     9
6     1
8     8
9     2
10    4
11    2
dtype: int64

Answer 2

There is only 1 'column' of values. The first 'column' is the index. Docs are here

In [8]: s = Series([3,2,1],index=[1,3,2])

In [9]: s
Out[9]: 
1    3
3    2
2    1
dtype: int64

Sort by the index

In [10]: s.sort_index()
Out[10]: 
1    3
2    1
3    2
dtype: int64

Sort by values

In [11]: s.sort_values()
Out[11]: 
2    1
3    2
1    3
dtype: int64