In the context of Boolean operations, and also when expressions are
used by control flow statements, the following values are interpreted
-as false: \code{False}, \code{None}, numeric zero of all types, empty
-sequences (strings, tuples and lists), and empty mappings (dictionaries).
-All other values are interpreted as true.
+as false: \code{False}, \code{None}, numeric zero of all types, and empty
+strings and containers (including strings, tuples, lists, dictionaries,
+sets and frozensets). All other values are interpreted as true.
The operator \keyword{not} yields \code{True} if its argument is false,
\code{False} otherwise.