Lesson 103: Python String Formatting

Welcome to Lesson 103 of the Python Learning Lounge! In this lesson, we will cover various methods for formatting strings in Python.

Table of Contents

• Introduction
• String Formatting Methods
  • Old Style % Formatting
  • New Style .format() Method
  • f-Strings (Literal String Interpolation)
• Examples
• Exercises
• Conclusion

Introduction

String formatting is a crucial part of writing clean and readable code in Python. It allows you to create strings that include variable values, making your code more dynamic and versatile.

String Formatting Methods

Old Style % Formatting

The old style of string formatting uses the % operator. This method is less commonly used in modern Python code but is still worth knowing.

name = "Alice"
age = 30
formatted_string = "Hello, %s! You are %d years old." % (name, age)
print(formatted_string)

New Style .format() Method

The .format() method is more powerful and flexible than the old style. It uses curly braces {} as placeholders in the string.

name = "Alice"
age = 30
formatted_string = "Hello, {}! You are {} years old.".format(name, age)
print(formatted_string)

f-Strings (Literal String Interpolation)

Introduced in Python 3.6, f-strings are the most modern and preferred way of formatting strings. They provide a concise and readable syntax.

name = "Alice"
age = 30
formatted_string = f"Hello, {name}! You are {age} years old."
print(formatted_string)

Examples

Here are a few more examples of string formatting:

1. Using the old style % formatting:

   value = 42
   formatted_string = "The answer is %d." % value
   print(formatted_string)

2. Using the .format() method:

   temperature = 20.5
   formatted_string = "The temperature is {:.1f} degrees Celsius.".format(temperature)
   print(formatted_string)

3. Using f-strings:

   pi = 3.14159
   formatted_string = f"The value of pi is approximately {pi:.2f}."
   print(formatted_string)

Exercises

1. Write a string that includes your name and your favorite hobby using the old style % formatting.
2. Create a string that includes your age and the current year using the .format() method.
3. Use an f-string to create a string that includes your hometown and your favorite food.

Conclusion

String formatting is a fundamental skill for any Python programmer. By mastering these three methods, you'll be well-equipped to handle any string formatting task that comes your way.

Happy coding!

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