Python String Formatting: A Comprehensive Guide

String formatting in Python is the process of building a string representation dynamically by inserting the value of numeric expressions or variables into an existing string. Python provides several techniques for string formatting, including the % operator, the format() method, f-strings, and the String Template class. This guide explores each of these methods in detail.

1. Using the ‘%’ Operator

The % (modulo) operator, often referred to as the string formatting operator, is one of the oldest methods for string formatting in Python. It uses format specifiers like %s for strings, %d for integers, and %f for floating-point numbers.

Example: Formatting Strings with the ‘%’ Operator

name = "Vista Academy"
print("Welcome to %s!" % name)

Output:

Welcome to Vista Academy!

2. Using the format() Method

The format() method is a built-in method of the str class. It uses curly braces {} as placeholders, which are replaced by the values provided in the method’s arguments.

Example: Formatting Strings with the format() Method

str = "Welcome to {}"
print(str.format("Vista Academy"))

Output:

Welcome to Vista Academy

3. Using f-strings

f-strings, or formatted string literals, are a modern and efficient way to format strings in Python. They allow you to embed expressions directly inside string literals by prefixing the string with f and using curly braces {} as placeholders.

Example: Formatting Strings with f-strings

item1_price = 2500
item2_price = 300
total = f'Total: {item1_price + item2_price}'
print(total)

Output:

Total: 2800

4. Using the String Template Class

The String Template class, part of the string module, provides a simple way to format strings using placeholders defined by a dollar sign $ followed by an identifier.

Example: Formatting Strings with the String Template Class

from string import Template

# Defining template string
str = "Hello and Welcome to $name !"

# Creating Template object
templateObj = Template(str)

# Providing values
new_str = templateObj.substitute(name="Vista Academy")
print(new_str)

Output:

Hello and Welcome to Vista Academy !