python - Fastest way to get occurrence of each element -


i have large dataframe looking 

                                             name     country   ...  1                                            paul     germany 2                                            paul     germany 3                                          george     italy 3                                          george     italy    3                                          george     italy                        ... n                                            john     usa

i'm looking occurence of each element of name column, such has 

                                             name     country   count  1                                            paul     germany    2000 2                                          george     italy       500                           ... n                                            john     usa       40000

any idea optimal way ?

because quite long 

df['count'] = df.groupby(['name'])['name'].transform(pd.series.value_counts)

you can this:

df.groupby(['name', 'country']).size()

example:

import pandas pd  df = pd.dataframe.from_dict({'name' : ['paul', 'paul', 'george', 'george', 'george'],     'country': ['germany', 'italy','germany','italy','italy']})  df

output:

    country name 0   germany paul 1   italy   paul 2   germany george 3   italy   george 4   italy   george

group , count:

df.groupby(['name', 'country']).size()

output:

name    country george  germany    1         italy      2 paul    germany    1         italy      1

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