pandas DataFrame set_axis() and set_index()

In this pandas tutorial we will discuss about methods:

• set_axis() or set axis in pandas and
• set_index() or set index in pandas.

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Introduction

DataFrame in pandas is an two dimensional data structure that will store data in two dimensional format. One dimension refers to a row and second dimension refers to a column, So It will store the data in rows and columns.

We can able to create this DataFrame using DataFrame() method. But this is available in pandas module, so we have to import pandas module.

Syntax:

pandas.DataFrame(data)

Where, data is the input dataframe , The data can be a dictionary that stores list of values with specified key

 

Example: Create DataFrame

In this example, we will create dataframe with 4 rows and 4 columns with college data 

import pandas as pd

#create dataframe from the college data
data= pd.DataFrame({'college_id':['c-001','c-021','c-002','c-004'],

                    'college_name':["vignan university","vvit","RVR - JC","Andhra University"],

                   "college_address":["guntur","guntur","guntur","guntur"],

                    "Total Staff":[1200,3422,5644,670]

                   })

#display the dataframe
print(data)

Output: DataFrame is created below.

  college_id       college_name college_address  Total Staff
0      c-001  vignan university          guntur         1200
1      c-021               vvit          guntur         3422
2      c-002           RVR - JC          guntur         5644
3      c-004  Andhra University          guntur          670

set_axis() or set axis in pandas

set_axis() or set axis in pandas is used to assign the indices for rows/columns.

Syntax:

dataframe_input.set_axis(labels, axis)

where,

1. dataframe_input is the input dataframe
2. labels is the names for rows/columns taken through a list.
3. axis = 0 specifies row indices and axis=1 specify column indices

Example 1: set axis in pandas example - row indices

For the above dataframe, we will assign the row indices as ['A','B','C','D'].

import pandas as pd

#create dataframe from the college data
data= pd.DataFrame({'college_id':['c-001','c-021','c-002','c-004'],

                    'college_name':["vignan university","vvit","RVR - JC","Andhra University"],

                   "college_address":["guntur","guntur","guntur","guntur"],

                    "Total Staff":[1200,3422,5644,670]

                   })

#display the dataframe by adding row indices
print(data.set_axis(['A','B','C','D'],axis=0))

Output:

In the above code , we added labels to the rows - ['A','B','C','D'].

  college_id       college_name college_address  Total Staff
A      c-001  vignan university          guntur         1200
B      c-021               vvit          guntur         3422
C      c-002           RVR - JC          guntur         5644
D      c-004  Andhra University          guntur          670

Example 2: set axis in pandas example - column indices

For the above dataframe, we will assign the column indices as ['A','B','C','D'].

import pandas as pd

#create dataframe from the college data
data= pd.DataFrame({'college_id':['c-001','c-021','c-002','c-004'],

                    'college_name':["vignan university","vvit","RVR - JC","Andhra University"],

                   "college_address":["guntur","guntur","guntur","guntur"],

                    "Total Staff":[1200,3422,5644,670]

                   })

#display the dataframe by adding column indices
print(data.set_axis(['A','B','C','D'],axis=1))

Output:

In the above code , we added labels to the column - ['A','B','C','D'].

       A                  B       C     D
0  c-001  vignan university  guntur  1200
1  c-021               vvit  guntur  3422
2  c-002           RVR - JC  guntur  5644
3  c-004  Andhra University  guntur   670

---

set_index() or set index in pandas

This set index in pandas method is used to set the dataframe index with the existing column/s.

Syntax:

For single column:
dataframe_input.set_index('column_name')

For multiple columns:
dataframe_input.set_index(['columns'])

where,

1. dataframe_input is the input dataframe
2. column_name is the name of the column which act as index to the dataframe

Example 1: set index in pandas - column indices

In this example, we will assign college_address column as index.

import pandas as pd

#create dataframe from the college data
data= pd.DataFrame({'college_id':['c-001','c-021','c-002','c-004'],

                    'college_name':["vignan university","vvit","RVR - JC","Andhra University"],

                   "college_address":["guntur","guntur","guntur","guntur"],

                    "Total Staff":[1200,3422,5644,670]

                   })

#display the dataframe by setting college_address column as index
print(data.set_index('college_address'))

Output:

So for this dataframe 'college_address' column will be the index.

                college_id       college_name  Total Staff
college_address                                           
guntur               c-001  vignan university         1200
guntur               c-021               vvit         3422
guntur               c-002           RVR - JC         5644
guntur               c-004  Andhra University          670

Example 2: set index in pandas - multiple column indices

In this example, we will assign college_address,college_name and college_id columns as index.

import pandas as pd

#create dataframe from the college data
data= pd.DataFrame({'college_id':['c-001','c-021','c-002','c-004'],

                    'college_name':["vignan university","vvit","RVR - JC","Andhra University"],

                   "college_address":["guntur","guntur","guntur","guntur"],

                    "Total Staff":[1200,3422,5644,670]

                   })



print(data.set_index(['college_address','college_name','college_address']))

Output:

So for this dataframe college_address,college_name and college_id columns will be the index.

                                                  college_id  Total Staff
college_address college_name      college_address                        
guntur          vignan university guntur               c-001         1200
                vvit              guntur               c-021         3422
                RVR - JC          guntur               c-002         5644
                Andhra University guntur               c-004          670

This wraps up our session on set axis in pandas and set index in pandas.