GROUP BY SUM on pandas数据框

Question

DF：

a b class
0 0  +
0 1  +
1 0  -

预期产出：

group each column based on class value and find the count, 
as in taking column 'a' as example the count should be 2 
for class '+' and 1 for class '-'

代码：

grp = df.groupby(df.class, axis=1).sum()

得到我甚至不理解的错误。对熊猫来说，任何建议都会很棒。

Answer 1

试试这个：

print(sample.groupby('class').count())