Setting columns as MultiIndex in Pandas - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a MultiIndex in pandas?

A MultiIndex is a way to have multiple levels of labels on an axis (rows or columns) in a pandas DataFrame. It helps organize data with hierarchical structure.

beginner

How do you set columns as a MultiIndex using pandas?

You can set columns as a MultiIndex by assigning a list of tuples or a pandas MultiIndex object to the DataFrame's columns attribute.

intermediate

What pandas function helps create a MultiIndex from arrays or tuples?

The function pandas.MultiIndex.from_tuples() or pandas.MultiIndex.from_arrays() helps create a MultiIndex from tuples or arrays.

beginner

Why use MultiIndex columns in a DataFrame?

MultiIndex columns help organize complex data with multiple categories or levels, making it easier to select, group, and analyze data hierarchically.

beginner

Example: How to set columns as MultiIndex from a list of tuples?

Example code:<br>import pandas as pd<br>df = pd.DataFrame([[1,2],[3,4]])<br>df.columns = pd.MultiIndex.from_tuples([('A','one'), ('A','two')])<br>print(df)<br>This sets columns with two levels: 'A' and 'one'/'two'.

What does setting columns as MultiIndex allow you to do?

A Organize columns with multiple hierarchical levels

B Change row labels to numbers

C Convert DataFrame to a list

D Remove duplicate rows

MultiIndex columns let you have multiple levels of labels on columns, organizing data hierarchically.

Which pandas function creates a MultiIndex from tuples?

A pd.Series()

B pd.DataFrame()

C pd.MultiIndex.from_tuples()

D pd.read_csv()

pd.MultiIndex.from_tuples() creates a MultiIndex from a list of tuples.

How do you assign a MultiIndex to DataFrame columns?

A Assign a MultiIndex object to df.columns

B Assign a list of strings to df.index

C Use df.set_index() on rows

D Call df.to_multiindex()

You assign a MultiIndex object directly to df.columns to set MultiIndex columns.

What type of data structure is a MultiIndex?

A Flat list of column names

B Hierarchical index with multiple levels

C Single-level index

D Dictionary of columns

A MultiIndex is a hierarchical index with multiple levels for rows or columns.

Which of these is a valid way to create MultiIndex columns?

A df.columns = df.index

B df.columns = ['A', 'one']

C df.columns = 0

D df.columns = pd.MultiIndex.from_arrays([['A','A'], ['one','two']])

Using pd.MultiIndex.from_arrays with lists of labels creates MultiIndex columns.

Explain how to set columns as a MultiIndex in a pandas DataFrame and why it might be useful.

Think about how columns can have multiple levels of labels.

Describe the difference between a regular column index and a MultiIndex in pandas.

Consider how many labels each column has.