change the order of columns in pandas | sort columns in pandas | reindex in pandas

In this pandas tutorial, we will discuss several ways to:

• reindex in pandas,
• change the order of columns in pandas,
• sort columns in pandas dataframe,

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First lets go through the concept of creating and understanding pandas dataframe. Later we will check how to reindex columns in pandas dataframe.

 

DataFrame 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 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 Pandas dataframe

In this example, we will create a dataframe with 4 rows and 4 columns with college data and assign indices through index parameter.

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']

                   },index=['one','two','three','four'])

#display the dataframe
print(data)

Output: DataFrame is created below

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

Now lets talk about different methods to change the order of columns in pandas.

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Method 1 : change the order of columns in pandas using reindex()

reindex in pandas is used to change the order of columns by taking the column names as input in specified order.

 

So, it will take only one parameter. i.e columns in a list.

Syntax:

dataframe.reindex(columns=[columns....])

where,

1. dataframe is the input dataframe

2. columns is the parameter which will take list of columns to be arranged in the order.

 

Example: reindex columns in pandas dataframe using reindex()

In this reindex columns in pandas dataframe example, we will change the order of columns.

import pandas as pd
from tabulate import tabulate

#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']

                   },index=['one','two','three','four'])


# change the column order
data = data.reindex(columns=['college_address','college_name','college_id','Total Staff'])

#display the dataframe
print(data)

Output: After we reindex columns in pandas dataframe below result is obtained

We will change the order of columns in the following order - ['college_address','college_name','college_id','Total Staff']

 

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

In the above code, we arranged  the columns of the dataframe in the order - 'college_address','college_name','college_id','Total Staff' and display the entire dataframe.

 

sort columns in pandas dataframe

Using the above reindex in pandas method we can also change the order of columns alphabetically.

 

By passing sorted() method as a parameter in reindex() method, we can change the order.

Syntax:

dataframe.reindex(sorted(dataframe.columns), axis=1)

where,

1. dataframe is the input dataframe

2. sorted(dataframe.columns) is the method used to order the columns by taking columns method.

3. axis =1 specifies column.

 

Example: sort columns in pandas dataframe

Given below is code snippet that sort columns in pandas dataframe or change the order of columns alphabetically.

import pandas as pd
from tabulate import tabulate

#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']

                   },index=['one','two','three','four'])


# change the column order alphabetically
data = data.reindex(sorted(data.columns), axis=1)

#display the dataframe
print(data)

Output: sort columns in pandas dataframe alphabetically result

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

In the above code, we change the column order alphabetically

So the order will be Total Staff, college_address, college_id, college_name

 

This way we can change the order of columns in pandas and sort columns in pandas using reindex in pandas.