Stop Guessing Values: Master Python’s f-String Debugging

Introduction

Tired of sprinkling print statements everywhere just to peek at a variable’s content? In this quick tip we’ll show you Python’s f–string debugging feature, introduced in Python 3.8, that prints both the variable name and its value in a single, readable line. No manual string concatenation, no extra mental overhead – just drop an = inside the braces and let Python do the work.

The Core Syntax

The new f–string syntax is remarkably simple:

value = 42
print(f"{value=}")  # → value=42

Placing an equals sign after the expression inside the curly braces tells Python to evaluate the expression and prepend the source text (value) followed by = and the resulting value. This works with any valid expression, not just plain variables.

Real–World Use Cases

1. Inside Loops

When iterating, you often need to watch the loop variable and intermediate state:

for i in range(3):
    square = i * i
    print(f"{i=}, {square=}")

Output:

i=0, square=0
i=1, square=1
i=2, square=4

This keeps the loop body tidy while giving you instant visibility.

Best Practices & Pitfalls