F-strings in Python, introduced in Python 3.6, provide a concise and readable way to embed expressions directly within string literals. To create an f-string, prefix the string with f or F and use curly braces {} to include variables, expressions, or function calls.

Basic Syntax

name = "Alice"
age = 30
print(f"My name is {name} and I'm {age} years old.")

Output: My name is Alice and I'm 30 years old.

Formatting Specifiers

Use a colon : inside the braces to apply formatting. Common format specifiers include:

• :.2f → Format float to 2 decimal places

  pi = 3.14159
  print(f"Pi rounded to 2 decimals: {pi:.2f}")  # Output: Pi rounded to 2 decimals: 3.14

• :05d → Format integer with leading zeros to width 5

  num = 42
  print(f"Zero-padded: {num:05d}")  # Output: Zero-padded: 00042

Alignment and Padding

• :<width> → Left-align

• :>width → Right-align

• :^width → Center-align

text = "Python"
print(f"Left: '{text:<10}'")     # Output: Left: 'Python     '
print(f"Right: '{text:>10}'")    # Output: Right: '     Python'
print(f"Center: '{text:^10}'")   # Output: Center: '  Python  '

Advanced Features

• Self-documenting expressions (Python 3.8+): Use =

  x = 10
  print(f"{x=}")  # Output: x=10

• Expression evaluation: Embed any valid Python expression

  print(f"Sum: {2 + 3 * 4}")  # Output: Sum: 14

Key Benefits

• Faster than % formatting and .format()

• More readable and maintainable

• Supports any expression, including method calls and comprehensions

For full details, refer to the Python documentation on f-strings or the fstring.help cheat sheet.