grouper_example1.py

data = {'dates':
        ['2012-05-04',
         '2012-05-04',
         '2012-06-04',
         '2012-08-08'],
        'types':
        ['a',
         'a',
         'z',
         'z',],
        'some_col':
        ['n',
         'u',
         'q',
         '']
        }

df['dates'] = pd.to_datetime(df['dates'])

df = df[['dates', 'types']].groupby([pd.Grouper(key='dates')]).agg('count').reset_index()

df = df.rename(columns={'types:'count'})

print(df)
                        
"""
      dates  count
1 2012-06-04      1
2 2012-08-08      1
0 2012-05-04      2
"""