Ordered categories in Pandas - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is an ordered category in pandas?

An ordered category is a type of categorical data where the categories have a meaningful order or ranking, like 'low' < 'medium' < 'high'.

beginner

How do you create an ordered categorical column in pandas?

Use pd.Categorical() with the ordered=True parameter and specify the category order with the categories argument.

beginner

Why use ordered categories instead of strings or numbers?

Ordered categories save memory and allow meaningful comparisons like <, >, and sorting based on the order you define.

intermediate

What happens if you compare two ordered categorical values in pandas?

Pandas compares them based on the order you set, not alphabetically or numerically. For example, 'low' < 'high' if 'low' is before 'high' in the category order.

intermediate

How can you change the order of categories in an existing ordered categorical column?

Use the cat.reorder_categories() method with the new order list and ordered=True to update the order.

Which parameter makes a pandas categorical ordered?

A order='asc'

B ordered=True

C sort=True

D rank=True

The parameter ordered=True tells pandas the categories have a meaningful order.

What is the output type when you use pd.Categorical(['low', 'high'], categories=['low', 'medium', 'high'], ordered=True)?

A A pandas Series

B A numpy array

C A list

D An ordered categorical object

This creates an ordered categorical object with the specified categories and order.

If 'medium' is between 'low' and 'high' in order, what is the result of 'medium' > 'low'?

A True

B False

C Error

D Depends on data type

Because 'medium' comes after 'low' in the order, the comparison returns True.

How do ordered categories help in sorting data?

A They convert categories to numbers before sorting.

B They sort data randomly.

C They allow sorting based on the defined order, not alphabetically.

D They do not affect sorting.

Ordered categories let pandas sort data according to the category order you set.

Which method changes the order of categories in a pandas categorical column?

A cat.reorder_categories()

B cat.set_order()

C cat.sort_categories()

D cat.change_order()

The cat.reorder_categories() method updates the order of categories.

Explain what ordered categories are and why they are useful in pandas.

Think about how you rank things in real life, like sizes or ratings.

Describe how to create and modify an ordered categorical column in pandas.

Focus on the parameters and methods pandas provides.