熊猫-使用另一个数据框过滤数据框

Question

I have two data frames that have same length like this

df1: 
   density
1  1,45
2  3,87
3  4,35
4  2,87
5  0.74
6  9.34
7  3.087
8  0.28
9  6,47
10 5,59

The second data frame looks like this

df2:
  State
1  1
2  1
3  1
4  1
5  1
6  1
7  0
8  0
9  0
10 0

I want an output that looks like this which means filter df1 in order to keep only values where df2 is equal to 1 :

output: 
   density
1  1,45
2  3,87
3  4,35
4  2,87
5  0.74
6  9.34

How can I do that? Can you help me please.

Answer 1

这应该工作

df1[df2.State.astype(bool)]

Answer 2

Let's use boolean index:

df1[df2.eq(1).values]

Output:

  density
1    1,45
2    3,87
3    4,35
4    2,87
5    0.74
6    9.34