Compare pandas dataframes for common rows in two dataframes

Question

I have two data frames df-1 and df-2 like this,

import pandas as pd

raw_data = {'company': ['comp1', 'comp1', 'comp1', 'comp1', 'comp2', 'comp2', 'comp2', 'comp2', 'comp3', 'comp3', 'comp3', 'comp3'], 
        'region': ['1st', '1st', '2nd', '2nd', '1st', '1st', '2nd', '2nd','1st', '1st', '2nd', '2nd'], 
        'name': ['John', 'Jake', 'Alice', 'Mathew', 'Mark', 'Jacon', 'Ryan', 'Sone', 'Steve', 'Rooke', 'Rani', 'Alice'], 
        'preTestScore': [4, 24, 31, 2, 3, 4, 24, 31, 2, 3, 2, 3],
        'postTestScore': [25, 94, 57, 62, 70, 25, 94, 57, 62, 70, 62, 70]}
df1 = pd.DataFrame(raw_data, columns = ['company', 'region', 'name', 'preTestScore'])
print df1


raw_data = {'company': [ 'comp1', 'comp1', 'comp2', 'comp2', 'comp2', 'comp2', 'comp3', 'comp3', 'comp3'], 
        'region': [ '2nd', '2nd', '1st', '1st', '2nd', '2nd','1st', '1st', '2nd'], 
        'name': [ 'Alice', 'Mathew', 'Mark', 'Jacon', 'Ryan', 'Sone', 'Steve', 'Rooke', 'Rani', ], 
        'status': [ 'great', 'average', 'average', 'average', 'good', 'great', 'average', 'average', 'average']}
df2 = pd.DataFrame(raw_data, columns = ['company', 'region', 'name', 'status'])
print df2

How to find the rows of company, region and name in df-1 which is same as df-2. In other words, how to find the inner join with combination of all three columns.

Answer 1

It depends what you mean by

rows in df-1 which is same as df-2.

since the columns are not identical.

If you mean rows that have the same value for the intersection of columns, you can perform an inner join user merge:

In [13]: pd.merge(df1, df2, how='inner')
Out[13]: 
  company region    name  preTestScore   status
0   comp1    2nd   Alice            31    great
1   comp1    2nd  Mathew             2  average
2   comp2    1st    Mark             3  average
3   comp2    1st   Jacon             4  average
4   comp2    2nd    Ryan            24     good
5   comp2    2nd    Sone            31    great
6   comp3    1st   Steve             2  average
7   comp3    1st   Rooke             3  average
8   comp3    2nd    Rani             2  average

Edit

If you'd like greater control for the join columns, you can use the on, or left_on and right_on parameters of the merge function. If you don't, pandas will assume you mean the intersection of columns of the two dataframes.