nunique() for unique counts in Pandas - Mini Project: Build & Apply

Counting Unique Values with pandas nunique()

📖 Scenario: You work at a small bookstore. You have a list of books sold each day. You want to find out how many unique book titles were sold each day.

🎯 Goal: Build a small program using pandas to count unique book titles sold per day using the nunique() function.

📋 What You'll Learn

Create a pandas DataFrame with sales data including 'day' and 'book_title' columns.

Create a variable to hold the day to analyze.

Use nunique() to count unique book titles sold on that day.

Print the count of unique book titles sold on the chosen day.

💡 Why This Matters

🌍 Real World

Counting unique items sold or recorded is common in sales, inventory, and customer data analysis.

💼 Career

Data analysts and scientists often use <code>nunique()</code> to quickly find how many distinct values exist in a dataset column.

1

Create the sales data DataFrame

Create a pandas DataFrame called sales with two columns: 'day' and 'book_title'. Use these exact rows: 'Monday', 'Book A', 'Monday', 'Book B', 'Monday', 'Book A', 'Tuesday', 'Book C', 'Tuesday', 'Book B'.

Pandas

import pandas as pd
# Create the sales DataFrame with columns 'day' and 'book_title' and the exact rows
# Your code here

Need a hint?

Use pd.DataFrame with a dictionary for columns.

2

Set the day to analyze

Create a variable called selected_day and set it to the string 'Monday'.

Pandas

import pandas as pd
sales = pd.DataFrame({
    'day': ['Monday', 'Monday', 'Monday', 'Tuesday', 'Tuesday'],
    'book_title': ['Book A', 'Book B', 'Book A', 'Book C', 'Book B']
})
# Create the variable selected_day and set it to 'Monday'
# Your code here

Need a hint?

Just assign the string 'Monday' to selected_day.

3

Count unique book titles sold on the selected day

Create a variable called unique_count that stores the number of unique book_title values in sales where the day equals selected_day. Use the nunique() function.

Pandas

import pandas as pd
sales = pd.DataFrame({
    'day': ['Monday', 'Monday', 'Monday', 'Tuesday', 'Tuesday'],
    'book_title': ['Book A', 'Book B', 'Book A', 'Book C', 'Book B']
})
selected_day = 'Monday'
# Calculate unique_count using nunique() for book titles on selected_day
# Your code here

Need a hint?

Use sales.loc[sales['day'] == selected_day, 'book_title'].nunique() to count unique titles.

4

Print the unique book count

Print the value of unique_count.

Pandas

import pandas as pd
sales = pd.DataFrame({
    'day': ['Monday', 'Monday', 'Monday', 'Tuesday', 'Tuesday'],
    'book_title': ['Book A', 'Book B', 'Book A', 'Book C', 'Book B']
})
selected_day = 'Monday'
unique_count = sales.loc[sales['day'] == selected_day, 'book_title'].nunique()
# Print unique_count
# Your code here

Need a hint?

Use print(unique_count) to show the result.