sort and count values in a column DataFrame (Python Pandas)

I have the next DataFrame

df

I count the values this way

I want to have the category values in the next order:

1.0 1

4.0 1

7.0 2

10.0 1

and so on …

In the ascending way with their respect amount of values

>Solution :

You can sort by index using sort_index()

df['col_1'].value_counts().sort_index()