Pandas - 如何按一个数字列分组并按每组的中位数过滤每组的行？

Question

I have a dataset consisting of one ID, one categorical variable "A" and one numerical variable "B".
I want to group by "A" and filter the rows from each group to get only the rows that are avobe or equal to the median of "B" (the median should be calculated for each group).
Example:

ID	A	B
1	Category 1	0.5
2	Category 2	0.2
3	Category 1	0.2
4	Category 1	0.6
5	Category 2	0.4

My expected result would be:

ID	A	B
1	Category 1	0.5
4	Category 1	0.6
5	Category 2	0.4

Being the median of category 1 = 0.5 and 0.3 for category 2.
Thank you!

Answer 1

out = df[df.groupby("A")["B"].transform(lambda x: x >= x.median())]
print(out)

Prints:

   ID           A    B
0   1  Category 1  0.5
3   4  Category 1  0.6
4   5  Category 2  0.4