A string conversion is an expression list enclosed in reverse (a.k.a. backward) quotes:
string_conversion: "`" expression_list "`"
A string conversion evaluates the contained expression list and converts the resulting object into a string according to rules specific to its type.
If the object is a string, a number, None, or a tuple, list or dictionary containing only objects whose type is one of these, the resulting string is a valid Python expression which can be passed to the built-in function eval() to yield an expression with the same value (or an approximation, if floating point numbers are involved).
(In particular, converting a string adds quotes around it and converts ``funny'' characters to escape sequences that are safe to print.)
It is illegal to attempt to convert recursive objects (e.g., lists or dictionaries that contain a reference to themselves, directly or indirectly.)
The built-in function repr() performs exactly the same conversion in its argument as enclosing it in parentheses and reverse quotes does. The built-in function str() performs a similar but more user-friendly conversion.