Pandas get total of consecutive rows in extra column

I try to get the count of the consecutive rows in an extra column.

Example of what I would like to have:

class    consecutive_count
a         3
a         3
a         3
b         2
b         2
c         1
d         1 
e         3
e         3
e         3
f         1
a         1
c         1
d         2
d         2

Best try is:

1. df['consecutive_count'] = df.groupby('class')['class'].transform('count')

Which gives the total count in de complete dataframe but does not count consecutive rows but total:

class    consecutive_count
a         4
a         4
a         4
b         2
b         2
c         2
d         3 
e         3
e         3
e         3
f         1
a         4
c         2
d         3
d         3

2. Using cumsum: df['consecutive-count'] = (df['class'] != df['class'].shift()).cumsum()

Which kind of groups the consecutive rows:

class    consecutive_count
a         1
a         1
a         1
b         2
b         2
c         3
d         4 
e         5
e         5
e         5
f         6
a         7
c         8
d         9
d         9

I really have no clue how to solve this.

>Solution :

You’re close with your second attempt.

df['consecutive_count'] = df.groupby(['class', (df['class']!=df['class'].shift()).cumsum()]).transform('size')

   class  consecutive_count
0      a                  3
1      a                  3
2      a                  3
3      b                  2
4      b                  2
5      c                  1
6      d                  1
7      e                  3
8      e                  3
9      e                  3
10     f                  1
11     a                  1
12     c                  1
13     d                  2
14     d                  2