Python Pandas Groupby按类别占总数的百分比

我有下表：

+-----+----------+---+
| Grp | Category | X |
+-----+----------+---+
|   1 | A        | 1 |
|   1 | B        | 3 |
|   1 | B        | 2 |
|   1 | C        | 2 |
|   2 | A        | 2 |
|   2 | A        | 4 |
|   2 | B        | 4 |
|   3 | A        | 3 |
|   3 | C        | 7 |
+-----+----------+---+

并尝试获得以下信息：

+-----+----------+---------+
| Grp | Category | X_ratio |
+-----+----------+---------+
|   1 | A        | 1/8     |
|   1 | B        | 5/8     |
|   1 | C        | 2/8     |
|   2 | A        | 6/10    |
|   2 | B        | 4/10    |
|   3 | A        | 3/10    |
|   3 | C        | 7/10    |
+-----+----------+---------+

还有一点卡住。 库德有人建议有效的解决方案？