Loop or Iterate over all or certain columns of a dataframe in Python-Pandas

In this article, we will discuss how to loop or Iterate overall or certain columns of a DataFrame? There are various methods to achieve this task.
Let’s first create a Dataframe and see that : 
Code : 

Python3

# import pandas package
import pandas as pd

# List of Tuples
students = [('Ankit', 22, 'A'),
           ('Swapnil', 22, 'B'),
           ('Priya', 22, 'B'),
           ('Shivangi', 22, 'B'),
            ]
# Create a DataFrame object
stu_df = pd.DataFrame(students, columns =['Name', 'Age', 'Section'],
                      index =['1', '2', '3', '4'])

stu_df

Output :

Now let’s see different ways of iterate or certain columns of a DataFrame :
Method #1: Using DataFrame.iteritems():
Dataframe class provides a member function iteritems() which gives an iterator that can be utilized to iterate over all the columns of a data frame. For every column in the Dataframe it returns an iterator to the tuple containing the column name and its contents as series.
Code : 

Python3

import pandas as pd


# List of Tuples
students = [('Ankit', 22, 'A'),
           ('Swapnil', 22, 'B'),
           ('Priya', 22, 'B'),
           ('Shivangi', 22, 'B'),
            ]

# Create a DataFrame object
stu_df = pd.DataFrame(students, columns =['Name', 'Age', 'Section'],
                      index =['1', '2', '3', '4'])

# gives a tuple of column name and series
# for each column in the dataframe
for (columnName, columnData) in stu_df.iteritems():
    print('Column Name : ', columnName)
    print('Column Contents : ', columnData.values)

Output:

Method #2: Using [ ] operator :
We can iterate over column names and select our desired column. 
Code : 

Python3

import pandas as pd


# List of Tuples
students = [('Ankit', 22, 'A'),
           ('Swapnil', 22, 'B'),
           ('Priya', 22, 'B'),
           ('Shivangi', 22, 'B'),
            ]

# Create a DataFrame object
stu_df = pd.DataFrame(students, columns =['Name', 'Age', 'Section'],
                      index =['1', '2', '3', '4'])

# Iterate over column names
for column in stu_df:

    # Select column contents by column
    # name using [] operator
    columnSeriesObj = stu_df[column]
    print('Column Name : ', column)
    print('Column Contents : ', columnSeriesObj.values)

Output:

Method #3: Iterate over more than one column :
Assume we need to iterate more than one column. In order to do that we can choose more than one column from dataframe and iterate over them.
Code : 

Python3

import pandas as pd


# List of Tuples
students = [('Ankit', 22, 'A'),
           ('Swapnil', 22, 'B'),
           ('Priya', 22, 'B'),
           ('Shivangi', 22, 'B'),
            ]

# Create a DataFrame object
stu_df = pd.DataFrame(students, columns =['Name', 'Age', 'Section'],
                      index =['1', '2', '3', '4'])

# Iterate over two given columns
# only from the dataframe
for column in stu_df[['Name', 'Section']]:

    # Select column contents by column
    # name using [] operator
    columnSeriesObj = stu_df[column]
    print('Column Name : ', column)
    print('Column Contents : ', columnSeriesObj.values)

Output:

Method #4: Iterating columns in reverse order :
We can iterate over columns in reverse order as well.
Code : 

Python3

import pandas as pd


# List of Tuples
students = [('Ankit', 22, 'A'),
           ('Swapnil', 22, 'B'),
           ('Priya', 22, 'B'),
           ('Shivangi', 22, 'B'),
            ]

# Create a DataFrame object
stu_df = pd.DataFrame(students, columns =['Name', 'Age', 'Section'],
                       index =['1', '2', '3', '4'])


# Iterate over the sequence of column names
# in reverse order
for column in reversed(stu_df.columns):

    # Select column contents by column
    # name using [] operator
    columnSeriesObj = stu_df[column]
    print('Column Name : ', column)
    print('Column Contents : ', columnSeriesObj.values)

Output:

Method #5: Using index (iloc) :
To iterate over the columns of a Dataframe by index we can iterate over a range i.e. 0 to Max number of columns than for each index we can select the contents of the column using iloc[]. 
Code : 

Python3

import pandas as pd


# List of Tuples
students = [('Ankit', 22, 'A'),
           ('Swapnil', 22, 'B'),
           ('Priya', 22, 'B'),
           ('Shivangi', 22, 'B'),
            ]

# Create a DataFrame object
stu_df = pd.DataFrame(students, columns =['Name', 'Age', 'Section'],
                      index =['1', '2', '3', '4'])


# Iterate over the index range from
# 0 to max number of columns in dataframe
for index in range(stu_df.shape[1]):

    print('Column Number : ', index)

    # Select column by index position using iloc[]
    columnSeriesObj = stu_df.iloc[:, index]
    print('Column Contents : ', columnSeriesObj.values)

Output: