Python Pandas Add column to DataFrame columns

ython Pandas Add column to DataFrame columns with What is Python Pandas, Reading Multiple Files, Null values, Multiple index, Application, Application Basics, Resampling, Plotting the data, Moving windows functions, Series, Read the file, Data operations, Filter Data etc.

<< Back to PYTHON

next → ← prev

Add a column to DataFrame Columns

We can add a new column to an existing DataFrame using different ways. For the demonstration, first, we have to write a code to read the existing file, which consists of some columns in a DataFrame.

import pandas as pd
aa = pd.read_csv("aa.csv")
aa.head()

The above code read the existing csv file and shows the data values column as the output.

Output



	Name
	Hire Date
	Salary
	Leaves Remaining


	0 John Idle
	03/15/14
	50000.0
	10


	1 Smith Gilliam
	06/01/15
	65000.0
	8


	2 Parker Chapman
	05/12/14
	45000.0
	10


	3 Jones Palin
	11/01/13
	70000.0
	3


	4 Terry Gilliam
	08/12/14
	48000.0
	7


	5 Michael Palin
	05/23/13
	66000.0
	8

Add new columns to a DataFrame using [] operator

If we want to add any new column at the end of the table, we have to use the [] operator. Let's add a new column named "Age" into "aa" csv file.

import pandas as pd
aa = pd.read_csv("aa.csv")
aa["Age"] = "24"
aa.head()

This code adds a column "Age" at the end of the aa csv file. So, the new table after adding a column will look like this:

    Name           Hire Date    Salary    Leaves Remaining  Age
0  John Idle        03/15/14    50000.0     10              24
1  Smith Gilliam    06/01/15    65000.0     8               24 
2  Parker Chapman   05/12/14    45000.0     10              24
3  Jones Palin      11/01/13    70000.0     3               24
4  Terry Gilliam    08/12/14    48000.0     7               24
5  Michael Palin    05/23/13    66000.0     8               24

In the above code, Age value has defined the universal value that means its value is common to all the rows. If we specify a column name that does not exist, Pandas will throw an error.

For ex:

aa["Designation"]

In the above code, Pandas will throw an error because the Designation column does not exist.

But if we assign a value to that column, Pandas will generate a new column automatically at the end of the table.

Add new columns in a DataFrame using insert()

We can also add a new column at any position in an existing DataFrame using a method name insert.

For the demonstration, first, we have to write a code to read the existing file that consists of some columns in a DataFrame.

import pandas as pd
aa = pd.read_csv("aa.csv")
aa.head()s

The above code read the existing csv file and shown the data values column in the output.

Output

    Name           Hire Date   Salary    Leaves Remaining
0  John Idle       03/15/14    50000.0    10
1  Smith Gilliam   06/01/15    65000.0    8
2  Parker Chapman  05/12/14    45000.0    10
3  Jones Palin     11/01/13    70000.0    3
4  Terry Gilliam   08/12/14    48000.0    7
5  Michael Palin   05/23/13    66000.0    8

Let's add a new column name "Department" into an existing "aa" csv file using insert method.

import pandas as pd
aa = pd.read_csv("aa.csv")
aa.insert(2, column = "Department", value = "B.Sc")
aa.head()

Output

   Name            Hire Date   Department   Salary    Leaves Remaining
0  John Idle       03/15/14     B.Sc        50000.0    10
1  Smith Gilliam   06/01/15     B.Sc        65000.0    8
2  Parker Chapman  05/12/14     B.Sc        45000.0    10
3  Jones Palin     11/01/13     B.Sc        70000.0    3
4  Terry Gilliam   08/12/14     B.Sc        48000.0    7
5  Michael Palin   05/23/13     B.Sc        66000.0    8

Next TopicDataFrame to Numpy Array

← prev next →

.Net

.NET Array Dictionary List String 2D Async DataTable Dates DateTime Enum File For Foreach Format IEnumerable If IndexOf Lambda LINQ Parse Path Process Property Regex Replace Sort Split Static StringBuilder Substring Switch Tuple

Java

Core Array ArrayList HashMap String 2D Cast Character Console Deque Duplicates File For Format HashSet If IndexOf Lambda Math ParseInt Process Random Regex Replace Sort Split StringBuilder Substring Switch Vector While

TheDeveloperBlog.com

Python Pandas Add column to DataFrame columns

Add a column to DataFrame Columns

Add new columns to a DataFrame using [] operator

Add new columns in a DataFrame using insert()

Related Links:

.Net

Java

Related Links