Get the rows where they have the same value of the column

Question

I have two dataframes ch2 and ch3 with an allele column ( I have more ch2 than ch3). I want to have the rows when both dataframes have the same value.

I have tried this code but every time I get FALSE as result. THANKS

for y in ch2.allele:
    print(y)
    i = ch3.allele
    print(i)
    testtt =(y in i)
    print (testt)
    if (testtt ==True):
        print ("ok")