Count appearances of a value until it changes to another value

Question

I have the following DataFrame:

df = pd.DataFrame([10, 10, 23, 23, 9, 9, 9, 10, 10, 10, 10, 12], columns=[\'values\'])

I want to calculate

Answer 1

You can keep track of where the changes in df['values'] occur, and groupby the changes and also df['values'] (to keep them as index) computing the size of each group

changes = df['values'].diff().ne(0).cumsum()
df.groupby([changes,'values']).size().reset_index(level=0, drop=True)

 values
10    2
23    2
9     3
10    4
12    1
dtype: int64