f-string-percent-format (RUF073)

Preview (since 0.15.8) · Related issues · View source

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What it does

Checks for uses of the % operator on f-strings.

Why is this bad?

F-strings already support interpolation via {...} expressions. Using the % operator on an f-string is almost certainly a mistake, since the f-string's interpolation and %-formatting serve the same purpose. This typically indicates that the developer intended to use either an f-string or %-formatting, but not both.

Example

f"{name}" % name
f"hello %s %s" % (first, second)

Use instead:

f"{name}"
f"hello {first} {second}"