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Adding a new column to existing DataFrame in Pandas in Python
In this tutorial, we are going to learn how to add a new column to the existing DataFrame in pandas. We can have different methods to add a new column. Let's all of them.
Using List
We can add a new column using the list. Follow the steps to add a new column.
Algorithm
1. Create DataFrame using a dictionary. 2. Create a list containing new column data. Make sure that the length of the list matches the length of the data which is already present in the data frame. 3. Add the list to the DataFrame like dictionary element.
Let's see one example.
Example
# importing pandas import pandas as pd # creating a DataFrame data = { 'Name': ['Hafeez', 'Aslan', 'Kareem'], 'Age': [19, 18, 15], 'Profession': ['Pythoneer', 'Programmer', 'Student'] } dataframe = pd.DataFrame(data) print('-----------Before adding a new column----------') print(dataframe) print('\n\n') # creating a list for new column places = ['Nellore', 'Mumbai', 'Andhra'] # we are using 'Places' as column name # adding the list to the dataframe as column dataframe['Places'] = places print('---------------After adding a new column------------') print(dataframe)
Output
If you run the above program you will get the following results.
-----------Before adding a new column---------- Name Age Profession 0 Hafeez 19 Pythoneer 1 Aslan 18 Programmer 2 Kareem 15 Student ---------------After adding a new column------------ Name Age Profession Places 0 Hafeez 19 Pythoneer Nellore 1 Aslan 18 Programmer Mumbai 2 K areem 15 Student Andhra
DataFrame.insert()
There is a built-in method called insert() to add a new column. Steps to follow.
Algorithm
1. Create DataFrame using dictionary. 2. Create a list containing new column data. Make sure that the length of the list matches the length of the data which is already present in the data frame. 3. Insert the data into the DataFrame using DataFrame.insert(index, column_name, data) method.
Example
# importing pandas import pandas as pd # creating a DataFrame data = { 'Name': ['Hafeez', 'Aslan', 'Kareem'], 'Age': [19, 18, 15], 'Profession': ['Pythoneer', 'Programmer', 'Student'] } dataframe = pd.DataFrame(data) print('-----------Before adding a new column----------') print(dataframe) print('\n\n') # creating a list for new column places = ['Nellore', 'Mumbai', 'Andhra'] # we are using 'Places' as column name # adding the list to the dataframe as column using insert(index, column_name, data) dataframe.insert(2, 'Places', places) print('---------------After adding a new column------------') print(dataframe)
Output
If you run the above program, you will get the following results.
-----------Before adding a new column---------- Name Age Profession 0 Hafeez 19 Pythoneer 1 Aslan 18 Programmer 2 Kareem 15 Student ---------------After adding a new column------------ Name Age Places Profession 0 Hafeez 19 Nellore Pythoneer 1 Aslan 18 Mumbai Programmer 2 Kareem 15 Andhra Student
DataFrame.assign()
This method takes one argument i.e., a list of data and adds it to the data frame as a column at the end.
Algorithm
1. Create DataFrame using a dictionary. 2. Create a list containing new column data. Make sure that the length of the list matches the length of the data which is already present in the data frame. 3. Insert the data into the DataFrame using DataFrame.assign(column_name = data) method. It returns a new data frame. So, we have to store it. 4. Print the new data frame.
Let's see an example.
Example
# importing pandas import pandas as pd # creating a DataFrame data = { 'Name': ['Hafeez', 'Aslan', 'Kareem'], 'Age': [19, 18, 15], 'Profession': ['Pythoneer', 'Programmer', 'Student'] } dataframe = pd.DataFrame(data) print('-----------Before adding a new column----------') print(dataframe) print('\n\n') # creating a list for new column places = ['Nellore', 'Mumbai', 'Andhra'] # we are using 'Places' as column name # adding the list to the dataframe as column using assign(column_name = data) new_dataframe = dataframe.assign(Places = places) print('---------------After adding a new column------------') print(new_dataframe)
Output
If you run the above program, you will get the following results.
-----------Before adding a new column---------- Name Age Profession 0 Hafeez 19 Pythoneer 1 Aslan 18 Programmer 2 Kareem 15 Student ---------------After adding a new column------------ Name Age Profession Places 0 Hafeez 19 Pythoneer Nellore 1 Aslan 18 Programmer Mumbai 2 Kareem 15 Student Andhra
Conclusion
If you have any doubts regarding the tutorial, mention them in the comment section.
Updated on: 26-Aug-2023
34K+ Views
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