Fastest way to merge pandas dataframe on ranges

Question

I have a dataframe A

    ip_address
0   13
1   5
2   20
3   11
.. ........

and another dataframe B

Answer 1

Try pd.merge_asof

df['lowerbound_ip_address']=df['ip_address']
pd.merge_asof(df1,df,on='lowerbound_ip_address',direction ='forward',allow_exact_matches =False)
Out[811]: 
   lowerbound_ip_address  upperbound_ip_address    country  ip_address
0                      0                     10  Australia           5
1                     11                     20      China          13