Pandas, groupby and finding maximum in groups

gistfile1.txt

#!/usr/local/bin/python2.7
    
import numpy as np
import pandas as pd

df_logfile = pd.DataFrame({ 'host'     : ['this.com', 'this.com', 'this.com', 'that.com', 'other.net', 'other.net', 'other.net'],
                             'service' : ['mail',     'mail',     'web',      'mail',     'mail',      'web',        'web'     ] })

print "Input"
print df_logfile

df = df_logfile.groupby(['host','service']).agg({'service':np.size})
df_count = pd.DataFrame()
df_count['host'] = df_logfile['host'].unique()
df_count['service']  = np.nan
df_count['no']    = np.nan

for h,data in df.groupby(level=0):
  i = data.idxmax()[0]   
  service = i[1]             
  no = data.xs(i)[0]
  df_count.loc[df_count['host'] == h, 'service'] = service
  df_count.loc[(df_count['host'] == h) & (df_count['service'] == service), 'no']   = no

print "\nOutput"
print df_count