String formatting using f-strings in Python - Mini Project: Build & Apply

String formatting using f-strings

📖 Scenario: You are creating a simple program to display information about a book in a friendly way. You want to show the book's title, author, and year of publication in a sentence.

🎯 Goal: Build a program that uses f-strings to format and display a sentence with the book's details.

📋 What You'll Learn

Create variables for the book's title, author, and year.

Create a variable for a short message prefix.

Use an f-string to combine the variables into a full sentence.

Print the formatted sentence.

💡 Why This Matters

🌍 Real World

Formatting strings nicely is useful for showing information clearly in apps, reports, or messages.

💼 Career

Many programming jobs require creating readable output for users, and f-strings make this easy and clean.

1

Create variables for book details

Create three variables: title with the value "The Great Gatsby", author with the value "F. Scott Fitzgerald", and year with the value 1925.

Python

# Your code here

Hint

Use simple assignment statements to create the variables with the exact names and values.

2

Create a message prefix variable

Create a variable called message and set it to the string "Book Info:".

Python

title = "The Great Gatsby"
author = "F. Scott Fitzgerald"
year = 1925
# Your code here

Hint

Just assign the string to the variable message.

3

Create a formatted string using f-string

Create a variable called formatted that uses an f-string to combine message, title, author, and year into this exact sentence: Book Info: "The Great Gatsby" by F. Scott Fitzgerald, published in 1925.

Python

title = "The Great Gatsby"
author = "F. Scott Fitzgerald"
year = 1925
message = "Book Info:"
# Your code here

Hint

Use an f-string with curly braces to insert the variables inside the string.

4

Print the formatted string

Write a print statement to display the formatted string.

Python

title = "The Great Gatsby"
author = "F. Scott Fitzgerald"
year = 1925
message = "Book Info:"
formatted = f'{message} "{title}" by {author}, published in {year}.'
# Your code here

Hint

Use print(formatted) to show the final sentence.

Practice

1. What is the main purpose of using f-strings in Python?

easy

A. To easily insert variables or expressions inside strings

B. To create lists from strings

C. To convert strings to uppercase

D. To repeat strings multiple times

Solution

1. Step 1: Understand f-string usage

   F-strings allow embedding variables or expressions inside strings using curly braces {}.

2. Step 2: Compare options

   Only To easily insert variables or expressions inside strings describes this purpose correctly; others describe unrelated string operations.

3. Final Answer:

   To easily insert variables or expressions inside strings -> Option A

4. Quick Check:

   f-strings = insert variables in strings [OK]

Hint: Remember: f-strings embed variables with curly braces {} [OK]

Common Mistakes:

• Confusing f-strings with string methods like upper()
• Thinking f-strings create lists
• Assuming f-strings repeat strings

2. Which of the following is the correct syntax to use an f-string to insert variable name into a string?

easy

A. "Hello, $name!"

B. f"Hello, {name}!"

C. f'Hello, $name!'

D. "Hello, {name}!"

Solution

1. Step 1: Identify f-string syntax

   An f-string starts with the letter f before the quotes and uses curly braces {} to insert variables.

2. Step 2: Check each option

   f"Hello, {name}!" correctly uses f"Hello, {name}!". Options A and B lack the f prefix, and C uses incorrect syntax with $name.

3. Final Answer:

   f"Hello, {name}!" -> Option B

4. Quick Check:

   f-string = f"text {var}" [OK]

Hint: f-string must start with f and use {variable} inside quotes [OK]

Common Mistakes:

• Omitting the f before the string
• Using $ instead of curly braces
• Using single quotes without f prefix

3. What will be the output of this code?

name = "Alice"
age = 30
print(f"{name} is {age} years old.")

medium

A. name is age years old.

B. {name} is {age} years old.

C. SyntaxError

D. Alice is 30 years old.

Solution

1. Step 1: Evaluate variables inside f-string

   The variables name and age are replaced by their values "Alice" and 30 inside the string.

2. Step 2: Understand print output

   The print statement outputs the string with variables replaced: "Alice is 30 years old.".

3. Final Answer:

   Alice is 30 years old. -> Option D

4. Quick Check:

   f-string replaces {name} and {age} with values [OK]

Hint: f-string prints variable values, not variable names [OK]

Common Mistakes:

• Expecting curly braces to print literally
• Confusing variable names with values
• Thinking f-string causes syntax error here

4. Find the error in this code snippet:

age = 25
print(f"Age is {age")

medium

A. Missing closing brace '}' in f-string

B. Missing f before the string

C. Variable age is not defined

D. Incorrect use of quotes

Solution

1. Step 1: Check f-string braces

   The f-string has an opening brace { but no matching closing brace }, causing a syntax error.

2. Step 2: Verify other parts

   The f prefix is present, variable age is defined, and quotes are correct.

3. Final Answer:

   Missing closing brace '}' in f-string -> Option A

4. Quick Check:

   Every { must have a matching } in f-string [OK]

Hint: Count braces in f-string; each { needs a } [OK]

Common Mistakes:

• Forgetting to close curly braces
• Thinking missing f causes this error
• Assuming variable is undefined

5. You want to print the price of an item with 2 decimal places using f-strings. Which code correctly formats the price variable?

price = 9.8765
# Choose the correct print statement

hard

A. print(f"Price: ${price:2f}")

B. print(f"Price: ${price:.2}")

C. print(f"Price: ${price:.2f}")

D. print(f"Price: ${price:.2d}")

Solution

1. Step 1: Understand format specifier for decimals

   To format a float with 2 decimal places, use :.2f inside the curly braces.

2. Step 2: Check each option

   print(f"Price: ${price:.2f}") uses {price:.2f} correctly. print(f"Price: ${price:2f}") misses the dot, print(f"Price: ${price:.2}") misses the type specifier, and print(f"Price: ${price:.2d}") uses invalid d for decimals.

3. Final Answer:

   print(f"Price: ${price:.2f}") -> Option C

4. Quick Check:

   Use :.2f to format float with 2 decimals [OK]

Hint: Use :.2f inside {} to show 2 decimal places [OK]

Common Mistakes:

• Omitting the dot before precision
• Using integer format 'd' for floats
• Leaving out the type specifier