Marko Rauhamaa <ma...@pacujo.net> writes: > Alain Ketterlin <al...@universite-de-strasbourg.fr.invalid>: > >> Grant Edwards <invalid@invalid.invalid> writes: >> >> [...] >>> Or to be a bit obtuse: Python parameters are passed by value, but all >>> values are references. >> >> Exactly, that's a perfect description. There's is no need for a new >> name. As a corollary, all names (including "variables" and object >> attributes) are references. > > We are all confusing each other because of the word "reference" means so > many things. > > In Grant's explanation, a "reference" is a pointer, the invisible gluons > that bind, say, a variable to an object. > > In Alain's sentence a "reference" is a variable or any other "lvalue" > that can be bound to an object. > > Thus, the statement > > a[3] = 4 > > contains the reference[Alain] "a[3]". After the statement is executed, > the reference[Alain] contains a reference[Grant] to an int object 4.
You're right, my wording is imprecise, your interpretation is absolutely correct. > Now, is it useful to make the distinction and use the verb "contain?" > > Yes, it is. Consider these statements: > > a[0] = 4 > a[1] = 4 > a[2] = a[1] > > Now, "a[0]", "a[1]" and "a[2]" are three separate references[Alain]. > However between the three, they contain a maximum of two distinct > references[Grant], which can be ascertained with an "is" test: > > a[2] is a[1] > => True > > So while the references[Grant] are identical, the references[Alain] are > not. If I'm not mistaken, Python has no means of comparing the > identities of references[Alain]. Right. -- Alain. -- https://mail.python.org/mailman/listinfo/python-list
