CODESARRAY

Short note, by Codesarray, , 2 min read

Python f-string debugging: print the name and value with =

Put an equals sign after a name inside an f-string and Python prints the name, the equals sign and the value, so debug prints never need the name typed twice.

Python f-string debugging takes one character: put an = after a name inside the braces and the f-string prints the name and its value together. You stop typing the variable name twice in every debug print.

The name and the value

price = 4.5
count = 3
total = price * count
print(f"{price=}")
print(f"{count=}")
print(f"{total=}")
price=4.5
count=3
total=13.5

f"{price=}" prints the text you wrote (price), then the equals sign, then the value. The label always matches the code, so a debug print cannot say prise while showing price.

It works on expressions

print(f"{price * count=}")
price * count=13.5

Whatever you write before the = is printed as written and then evaluated, so you see both the expression and its result.

When to use it

  • Quick debug prints while you work out why a value is wrong.
  • Checking an intermediate calculation without naming it.
  • It needs Python 3.8 or later.

Because the print is one short line, it is also easy to delete when you are done.

This is a short note on Strings, lesson 4 of the Python beginner track.

This article goes with the video Debug with an f-string equals sign. Watch it on YouTube.