percent-format-mixed-positional-and-named (F506)

Derived from the Pyflakes linter.

What it does

Checks for printf-style format strings that have mixed positional and named placeholders.

Why is this bad?

Python does not support mixing positional and named placeholders in printf-style format strings. The use of mixed placeholders will raise a TypeError at runtime.

Example

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

Use instead:

"%s, %s" % ("Hello", "World")

Or:

"%(greeting)s, %(name)s" % {"greeting": "Hello", "name": "World"}

References

• Python documentation: printf-style String Formatting