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Python Academy · Lesson

String Formatting with f-strings

Use f-strings and format() for clean, readable output.

Lesson 4 of 414 steps

String Formatting with f-strings is a free Python Academy lesson on CoddyKit. This is lesson 4 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the Python Academy learning path, and your progress syncs across the web and the CoddyKit app. The Python Academy course includes 4 lessons in total.

Introduction

F-strings (f'...') are Python's modern string interpolation syntax — fast, readable, and powerful.

Basic f-string

Prefix a string with f and put expressions in {}. f'Hello {name}' inserts the value of name inline.
name = 'Alice'
print(f'Hello {name}!')

Expressions in f-strings

Any Python expression works inside {}: f'{2 + 2}' gives '4'. f'{len(name)}' inserts the length.
x = 10
print(f'Square: {x**2}')

Format Specifiers

f'{3.14159:.2f}' rounds to 2 decimal places. f'{1000000:,}' adds comma separators.
pi = 3.14159
print(f'{pi:.2f}')
print(f'{1000000:,}')

Width and Alignment

f'{name:<20}' left-aligns in 20 chars. f'{name:>20}' right-aligns. f'{name:^20}' centers.
name = 'Alice'
print(f'{name:^20}')

Debug with =

f'{x=}' prints the expression and its value: 'x=42'. Perfect for quick debugging.
x = 42
print(f'{x=}')

The format() Method

'Hello {}'.format('World') works like f-strings but can be stored as templates. '{0} {1}'.format('a','b') uses positional args.
print('Hello {}'.format('World'))

The % Operator (Legacy)

'Hello %s, you are %d' % ('Alice', 30) is the old C-style formatting. Avoid in new code, but recognize it in legacy projects.
print('Hello %s, age %d' % ('Bob', 25))

Multi-line f-strings

Combine triple quotes and f: f'''Name: {name}\nAge: {age}''' for readable multi-line templates.
name, age = 'Alice', 30
print(f'Name: {name}\nAge: {age}')

Nested Quotes in f-strings

If the f-string uses single quotes, use double inside {}: f'Value: {d["key"]}'. Or use a temp variable to avoid confusion.
d = {'key': 'val'}
print(f'Value: {d["key"]}')

Performance of f-strings

F-strings are faster than .format() and % because they are evaluated at parse time. Prefer them in new code.

Quick Check

What does f'{x=}' print when x = 5?
Answer it in the interactive lesson

Recap

F-strings: f'{expr}' for interpolation, f'{x:.2f}' for formatting, f'{x=}' for debug output. Faster and more readable than % or .format().

Keep Going

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Frequently Asked Questions

Is the “String Formatting with f-strings” lesson free?

Yes — the full text of “String Formatting with f-strings” is free to read here on the web. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the Python Academy course, upgrade to CoddyKit PRO. The Python Academy course includes 4 lessons in total.

What will I learn in “String Formatting with f-strings”?

Use f-strings and format() for clean, readable output. You practise Python Academy with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.

Do I need any experience to start Python Academy?

No prior experience is required. Python Academy on CoddyKit is structured for beginners through advanced learners, so you can start here or from the beginning and move at your own pace. This is lesson 4 of 4.

How long does the “String Formatting with f-strings” lesson take?

Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.

Can I write and run code in this Python Academy lesson?

Yes. Every Python Academy lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.

All lessons in this course

  1. String Basics and Indexing
  2. String Slicing and Concatenation
  3. Common String Methods
  4. String Formatting with f-strings
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