# 分类下重复值
df_test = pd.DataFrame(
    data=np.array([
        [1]*3 + [2]*3,
        np.repeat([1,2,3], 2)
    ]).T,
    columns=['col'+str(i) for i in range(1,3)]
)
# https://blog.51cto.com/u_16055028/6177557 透视表 计数
display(df_test.pivot_table(
    index=['col1', 'col2'],
    values=['col2'],
    aggfunc=len
))  # 正确
display(df_test.pivot_table(
    index=['col1', 'col2'],
    values=['col2'],
    aggfunc='count'
))  # 无效?
display(df_test.pivot_table(
    index=['col1', 'col2'],
    values=['col2'],
    aggfunc=np.count_nonzero
))  # 忽略分组,忽略空字符串
# 以下均有效,必须新增列
df_test['计数'] = df_test['col2']
display(df_test.pivot_table(
    index=['col1', 'col2'],
    values=['计数'],
    aggfunc=len
))
display(df_test.pivot_table(
    index=['col1', 'col2'],
    values=['计数'],
    aggfunc='count'
))
display(df_test.pivot_table(
    index=['col1', 'col2'],
    values=['计数'],
    aggfunc=np.count_nonzero
))