On Thu, Sep 10, 2015, at 14:13, Steven D'Aprano wrote: > Because that's the definition of an expression in this context. An > expression is evaluated to either return a result, or raise an exception.
Nonsense. An expression is something allowed within a larger expression. It's easy to imagine an expression allowing a subexpression that does not return a result. For example, in non-tail positions of something like C-comma/Lisp-progn. Or, for example, if a C-style "for" loop was an expression, the initializer and increment bits. This is semantics, to some extent - you could just as well say an expression may "return" a "result" that is a special non-value which transforms into an error if it's allowed to escape into a context where the value is needed (e.g. the argument to a function, a place a boolean is expected, being assigned to a variable) - C (and other C-family languages) has such a thing, Lisp does not. -- https://mail.python.org/mailman/listinfo/python-list
