python - Pandas - 从行数中获取汇总数据框

Question

给定这个 DataFrame:

    bowl    cookie
0   one     chocolate
1   two     chocolate
2   two     chocolate
3   two     vanilla
4   one     vanilla
5   one     vanilla
6   one     vanilla
7   one     vanilla
8   one     vanilla
9   two     chocolate

我想获得以下总结的 DataFrame:

        vanilla     chocolate
one     5           1
two     1           3

除了手动进行:

vanilla_bowl1 = len(df_picks[(df_picks['bowl'] == 'one') & (df_picks['cookie'] == 'vanilla')])
vanilla_bowl2 = len(df_picks[(df_picks['bowl'] == 'two') & (df_picks['cookie'] == 'vanilla')])
chocolate_bowl1 = ...
chocolate_bowl2 = ...

有没有办法用 Pandas 在一次操作中做到这一点？

---

注意:我查看了 df.pivot()，如果我添加列 count 等于，这将起作用每行 1:

    bowl    cookie      count
0   one     chocolate       1
1   two     chocolate       1
2   two     chocolate       1
3   two     vanilla         1
4   one     vanilla         1
5   one     vanilla         1
6   one     vanilla         1
7   one     vanilla         1
8   one     vanilla         1
9   two     chocolate       1

然后

df.pivot(index='bowl', columns='cookie', values='count')

但是，我想知道是否有更直接的方法，不需要首先添加 count 列。

Answer 1

最简洁的方式可能是pandas.crosstab函数:

>>> pandas.crosstab(d.bowl, d.cookie)
cookie  chocolate  vanilla
bowl                      
one             1        5
two             3        1