percent-format-missing-argument (F505)

Derived from the Pyflakes linter.

What it does

Checks for named placeholders in printf-style format strings that are not present in the provided mapping.

Why is this bad?

Named placeholders that lack a corresponding value in the provided mapping will raise a KeyError.

Example

"%(greeting)s, %(name)s" % {"name": "world"}

Use instead:

"Hello, %(name)s" % {"name": "world"}

References

• Python documentation: printf-style String Formatting