How to Use f String in Python: Simple Guide with Examples

In Python, use f"..." to create an f string, which lets you insert variables or expressions inside curly braces {} directly in the string. This makes string formatting simple and readable without extra functions.

Syntax

An f string starts with the letter f or F before the opening quote. Inside the string, you put variables or expressions inside {}. Python replaces these with their values when the string runs.

• f"...": Marks the string as an f string.
• {variable}: Inserts the value of variable.
• {expression}: You can put any valid Python expression inside the braces.

python

name = "Alice"
age = 30
message = f"My name is {name} and I am {age} years old."
print(message)

Output

My name is Alice and I am 30 years old.

Example

This example shows how to use f strings to insert variables and do calculations inside the string easily.

python

price = 9.99
quantity = 5
total = price * quantity
receipt = f"Price: ${price}, Quantity: {quantity}, Total: ${total:.2f}"
print(receipt)

Output

Price: $9.99, Quantity: 5, Total: $49.95

Common Pitfalls

Some common mistakes when using f strings are:

• Forgetting the f before the string, so variables won't be replaced.
• Using single braces {} incorrectly or forgetting to close them.
• Trying to use backslashes inside expressions, which can cause errors.

python

name = "Bob"
# Wrong: missing f before string
message_wrong = "Hello, {name}!"
print(message_wrong)  # prints the literal text, not the variable

# Right:
message_right = f"Hello, {name}!"
print(message_right)

Output

Hello, {name}!
Hello, Bob!

Quick Reference

Use this quick guide to remember how to use f strings:

Feature	Usage Example	Description
Basic variable	f"Name: {name}"	Insert variable value inside braces
Expression	f"Sum: {a + b}"	Calculate inside braces
Format number	f"Price: {price:.2f}"	Format float to 2 decimals
Use quotes	f"He said, '{quote}'"	Mix quotes inside string
Multiline	f"""Line1 {var}\nLine2"""	Use triple quotes for multiline

Key Takeaways

Always start the string with f or F to enable variable insertion.

Put variables or expressions inside curly braces {} to include their values.

You can format numbers and expressions directly inside the braces.

Without the f prefix, variables inside braces won’t be replaced.

Use f strings for clear, readable, and concise string formatting.