Pandas DataFrame assign() Method

Preparation

Before any data manipulation can occur, two (2) new libraries will require installation.

• The Pandas library enables access to/from a DataFrame.
• The NumPy library supports multi-dimensional arrays and matrices in addition to a collection of mathematical functions.

To install these libraries, navigate to an IDE terminal. At the command prompt ($), execute the code below. For the terminal used in this example, the command prompt is a dollar sign ($). Your terminal prompt may be different.

$ pip install pandas

Hit the <Enter> key on the keyboard to start the installation process.

$ pip install numpy

Hit the <Enter> key on the keyboard to start the installation process.

If the installations were successful, a message displays in the terminal indicating the same.

FeFeel free to view the PyCharm installation guide for the required libraries.

• How to Install Pandas on PyCharm
• How to Install NumPy on PyCharm

Add the following code to the top of each code snippet. This snippet will allow the code in this article to run error-free.

import pandas as pd
import numpy

DataFrame assign()

The assign() method adds (assigns) column(s) to an existing DataFrame.

The syntax for this method is as follows:

DataFrame.assign(**kwargs)

For this example, a new column (accessed) adds to the DataFrame df_custs. The column fills in with random integer values. In a real-life, this column would keep track of how many times the user logged in to their account.

df_custs = pd.DataFrame({('jkende',  'Vzs*@4:kNq%)'), 
                         ('sarahJ',  '{M$*3zB~-a-W'), 
                         ('AmyKerr', '*7#<bSt?Y_Z<')}, 
                         columns=['username', 'password'], 
                         index=['user-a', 'user-b', 'user-c'])

result = df_custs.assign(accessed=pd.Series(np.random.randint(0,500,size=3)).values)
print(result)

• Line [1] creates a DataFrame from a Dictionary of Tuples and assigns it to df_custs.
• Line [2] assigns a new column (accessed) with random integers values to fill in this column. This output saves to result.
• Line [3] outputs result to the terminal.

Output

df_custs

💡 Note: The order of the records changes.

More Pandas DataFrame Methods

Feel free to learn more about the previous and next pandas DataFrame methods (alphabetically) here:

Also, check out the full cheat sheet overview of all Pandas DataFrame methods.