A printf-style format string (i.e. a string that is used as the left hand side of the % operator, such as fmt % arguments) must consist of valid conversion specifiers, such as %s, %d, etc. Otherwise, a ValueError will be raised.

Ensure a valid conversion specifier is used.

In the following example, format_as_tuple_incorrect, %t is not a valid conversion specifier.

Python Library Reference: printf-style String Formatting.