isin pandas retrieve null values

I am trying to find dataframe values exist in another dataframe, I used isin function but it retrieve only values for the first column. ex: df1 has 5 columns, and df2 has 10 columns. The output I need all rows from df2 depend on column B1 value in df2.
Example

df1

df2

The needed output

df3

I used the code :

df3_1 = df2[df2.B1.isin(df1.A1)]

df3_2 = df2[df2.B1.isin(df1.A2)]

df3_3 = df2[df2.B1.isin(df1.A3)]

only df3_1 has correct values ,df3_2 and df3_3 are empty. I don’t know the reason.

>Solution :

One reason should be traling spaces, try remove them, also convert values to lowercase:

s = df2.B1.str.strip().str.lower()
df3_2 = df2[s.isin(df1.A2.str.strip().str.lower())]
df3_3 = df2[s.isin(df1.A3.str.strip().str.lower())]