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f-Strings

f-strings (formatted string literals) are Python's modern, preferred way to embed expressions inside string literals. Prefixing a string with f lets you write variables and expressions directly inside curly braces, and Python evaluates and inserts them at runtime. f-strings also support format specifiers for controlling decimal places, padding, and alignment, making them more readable and faster than older formatting methods like %-formatting or .format().

Syntax

f"text {expression}"

Examples

Basic Interpolation

Embedding variable values directly inside a string.

name = "Fola"
age = 21
print(f"{name} is {age} years old")

Expressions Inside f-strings

f-strings can contain any valid expression, not just plain variable names.

a = 5
b = 3
print(f"{a} + {b} = {a + b}")

items = ["apple", "banana", "cherry"]
print(f"You have {len(items)} items")

user = {"name": "Priya"}
print(f"Hello, {user['name']}!")

Formatting Numbers

Using format specifiers to control decimal places, padding, and thousands separators.

price = 19.5
print(f"${price:.2f}")        # $19.50

number = 7
print(f"{number:03d}")        # 007

population = 1500000
print(f"{population:,}")      # 1,500,000

Multi-line f-strings

Combining f-strings with triple quotes for readable multi-line output.

name = "Fola"
role = "Developer"

profile = f"""
Name: {name}
Role: {role}
Status: Active
"""
print(profile)

Best practices

  • Prefer f-strings over %-formatting or .format() in modern Python - they are more readable and generally faster
  • Use format specifiers like :.2f for currency and :, for thousands separators instead of manual string manipulation
  • Keep expressions inside f-strings simple - if logic gets complex, compute the value in a variable first
  • Remember f-strings require Python 3.6 or later - check your target Python version if compatibility matters

At a glance

Purpose
Scripting and general-purpose applications
File extension
.py
Runs in
Python interpreter
Usually used with
Python standard library and packages

Specifications & further reading

Related Python documentation

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