group by counts pandas code example

Example 1: pandas groupby count as new column

In [12]: df.groupby(["item", "color"])["id"].count().reset_index(name="count")
Out[12]:
    item  color  count
0    car  black      2
1  truck   blue      1
2  truck    red      2

Example 2: pandas count values by column

df = pd.DataFrame({'a':list('abssbab')})
df.groupby('a').count()

Example 3: pandas count

>>> df.set_index(["Person", "Single"]).count(level="Person")
        Age
Person
John      2
Lewis     1
Myla      1

Example 4: group by pandas count

df[['col1', 'col2', 'col3', 'col4']].groupby(['col1', 'col2']).agg(['mean', 'count'])