f-Strings

Python’s f-strings (formatted string literals) provide a concise and efficient way to embed expressions and variables into strings. Introduced in Python 3.6, f-strings make string formatting easier and more readable.

Creating an f-String

To create an f-string:

1. Start the string with an f or F.
2. Use curly braces {} to include expressions or variables.

Example:

name = "Alice"
age = 30

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

Embedding Expressions

f-Strings can evaluate expressions directly within curly braces.

Example:

a = 5
b = 3

print(f"{a} + {b} = {a + b}")  # 5 + 3 = 8
print(f"The square of {a} is {a**2}.")  # The square of 5 is 25.

Formatting Numbers

f-Strings support number formatting for enhanced output:

Examples:

value = 12345.6789

# Round to 2 decimal places
print(f"Value: {value:.2f}")  # Value: 12345.68

# Add commas
print(f"Formatted: {value:,.2f}")  # Formatted: 12,345.68

# Percentage
percentage = 0.85
print(f"Success Rate: {percentage:.1%}")  # Success Rate: 85.0%

Multiline f-Strings

Use triple quotes for multiline f-strings:

name = "Alice"
age = 30

message = f"""
Name: {name}
Age: {age}
Status: {"Adult" if age >= 18 else "Minor"}
"""
print(message)

Using f-Strings with Functions

You can call functions directly within f-strings:

def greet(name):
    return f"Hello, {name}!"

print(f"{greet('Alice')} Welcome to Python.")  # Hello, Alice! Welcome to Python.

Escaping Braces in f-Strings

To include literal curly braces { or } in an f-string, double them:

print(f"{{}} is an empty set of braces.")  # {} is an empty set of braces.

Practice Exercises

1. Create variables for:
   • Your name.
   • Your favorite color.
   • Your favorite number. Use an f-string to print a sentence including all three variables.
2. Calculate and display the following using f-strings:
   • The area of a circle with a radius of 7 (use 3.14 for π).
   • A salary increase of 15% for an initial salary of $50,000.
3. Print a formatted table:
   • Product names and their prices.
   • Align product names to the left and prices to the right, formatted to two decimal places.

f-Strings are a powerful and convenient feature for dynamic string formatting in Python. They make your code cleaner and easier to read!