percent-format-unsupported-format-character (F509)

Derived from the Pyflakes linter.

What it does

Checks for printf-style format strings with invalid format characters.

Why is this bad?

In printf-style format strings, the % character is used to indicate placeholders. If a % character is not followed by a valid format character, it will raise a ValueError at runtime.

Example

"Hello, %S" % "world"

Use instead:

"Hello, %s" % "world"

References

• Python documentation: printf-style String Formatting