On Thu, 30 Oct 2008 19:55:57 -0700, Aaron Brady wrote: > On Oct 30, 9:05 pm, Steven D'Aprano <[EMAIL PROTECTED] > cybersource.com.au> wrote: >> On Fri, 31 Oct 2008 13:58:13 +1300, greg wrote: >> > Dale Roberts wrote: >> > snip >> >> > If they understand how assignment works in Python, that tells them >> > all they need to know. >> >> Nonsense. > > Maybe I missed this part. What does the phrase, "value of variable x" > mean in Python? Is it the same as what it means in C, Pascal, etc.? > > In other words, > >>>> x= [ 2, 3, 4 ] >>>> '0x%x'%id( x ) > '0xb39dd0' > > What is the value of 'x'? > a) [ 2, 3, 4 ] > b) An object with contents [ 2, 3, 4 ] > c) 0xb39dd0 > d) None of the above.
Solution a) is just shorthand for b), because there are (or at least could be) many such objects [2, 3, 4]. So I'd accept either a) or b) as reasonable answers. Solution c) is the answer that is required for "Python is call-by-value" to be correct. > If "value of 'x'" is not defined, we should agree on a definition that's > really clear and useful, favoring useful. The ordinary dictionary meaning is sufficient: "what is denoted by a symbol". > After that's established, we > can proceed to evaluating what 'call by value' would behave like, which > would then determine if Python behaves like it. Call by value is traditionally defined in at least some languages as meaning that a copy of the value of the parameter is passed to the function. Those languages include C and Pascal, and possibly Basic. I'd estimate that 80% of programmers over the last 40 years have had their understanding of "call by whatever" shaped by those three languages. > So, logically, if... she... weighs... the same as a duck,... she's made > of wood. Nice one :) -- Steven -- http://mail.python.org/mailman/listinfo/python-list
