Formatting Output with Python F-Strings

In Python, string formatting is a crucial aspect of working with text and data representation. While the .format() method has been a staple for a long time, the introduction of f-strings in Python 3.6 revolutionized the way we format strings. In this post, we’ll explore the power and flexibility of f-strings, highlighting their advantages over the legacy .format() method. You may be surprised at just how much f-strings are capable of!

Interpolation is the technical term for the kind of substitution performed by f-strings in Python. Basically we create a placeholder in our output which gets dynamically filled in with the value of the expression provided.

Legacy Method: .format()

Before diving into f-strings, let’s briefly touch upon the traditional string formatting approach using the .format() method. Here’s a quick example:

name = "John"
age = 30
height = 6.2

formatted_string = "Name: {}, Age: {}, Height: {}".format(name, age, height)


Name: John, Age: 30, Height: 6.2

F-strings: The Modern Solution

F-strings, short for “formatted string literals,” provide a concise and expressive way to embed expressions inside string literals. Let’s explore various scenarios and examples to illustrate their versatility.

Basic Examples

name = "John"
age = 30

# Basic f-string
formatted_string = f"Name: {name}, Age: {age}"


Name: John, Age: 30

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Expressions and Arithmetic

a = 5
b = 3

# Expressions inside f-string
result = f"The sum of {a} and {b} is {a + b}"


The sum of 5 and 3 is 8

Padding and Alignment

num = 42

# Right-aligned with 5 spaces
formatted_num = f"Number: {num:5}"

# Left-aligned with 8 spaces
formatted_num_left = f"Number: {num:<8}"


Number:    42
Number: 42  

Number of Digits for Float Display

pi = 3.141592653589793

# Display pi with 2 decimal places
formatted_pi = f"Pi: {pi:.2f}"


Pi: 3.14

Different Data Types

value = 42
percentage = 0.75
is_valid = True

# Handling different data types
formatted_data = f"Value: {value}, Percentage: {percentage}, Valid: {is_valid}"


Value: 42, Percentage: 0.75, Valid: True

Dictionary Access

person = {'name': 'Alice', 'age': 25}

# Accessing dictionary values
formatted_dict = f"Name: {person['name']}, Age: {person['age']}"


Name: Alice, Age: 25

Inline Function Calls

def double(x):
    return x * 2

number = 7

# Inline function call
formatted_result = f"Double of {number} is {double(number)}"


Double of 7 is 14


F-strings bring clarity, conciseness, and enhanced functionality to string formatting in Python. With their expressive syntax and diverse capabilities, they have become the preferred choice for many developers. Whether you’re a beginner or an experienced Pythonista, incorporating f-strings into your coding arsenal is a step towards more readable and efficient code.

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