I have a pandas dataframe in which I want to add a column (col_new), which values depend on a comparison of values in a existing column (col_exist).
Existing column (type=objects) contains As and Bs. New column should count, starting with 1. If an A follows an A, the count should rise by one. If an A follows a B, the count should rise by one. If a B follows an A, the count should not rise. If a B follows a B, the count should not rise.
col_exist col_new A 1 A 2 A 3 B 3 A 4 B 4 B 4 A 5 B 5
I am completely new to programming, so thank you in advance for your adequade answer.
df['col_new'] = df['col_exist'].eq('A').cumsum()
col_exist col_new 0 A 1 1 A 2 2 A 3 3 B 3 4 A 4 5 B 4 6 B 4 7 A 5 8 B 5