Just wrote: > In article <[EMAIL PROTECTED]>, > Larry Bates <[EMAIL PROTECTED]> wrote: > >> While I have never needed anything like this in my 5 years of Python >> programming, here is a way: >> >> a,b,c = 3*[0] >> q,r,s,t,u,v = 6*[0] > > This is (IMO) fairly idiomatic: > > a = b = c = 0 > q = r = s = t = u = v = 0 > > Just
You must be careful with this as they all point to exactly the same object. Example: >>> q = r = s = t = u = v = 0 >>> id(q) 3301924 >>> id(r) 3301924 >>> id(s) 3301924 >>> Notice that all of them point to exactly the same object, not 6 copies of zero which is "probably" what the poster was thinking. Most of the time when I see this, it is because people are thinking of variables having values which is mostly a carry-over from old Fortran/Cobol/Basic programming ideas. In python variables are pointers to objects. Objects could be values, but they are not placeholders where you store stuff. I read on this list (quite frequently) that people think they are getting 6 separate variables each with a zero stored in them. They are not. They are getting six pointers that all point to an integer zero (IMHO it would be a rather odd application for a programmer to want this). Here is where multiple assignments causes problems for beginners: >>> a=[] >>> b=c=a >>> a.append(6) >>> b [6] What?? 'b' should contain an empty list, right? Nope. a, b, and c all point to the SAME list just like the poster's q, r, s, t, u, v all point to the SAME zero. What they meant to write was: c=a[:] # Shallow copy of list b=a[:] My rule, don't do it unless you know exactly why you want to do it. It will trip you up at some point and be VERY hard to find. -Larry Bates -- http://mail.python.org/mailman/listinfo/python-list
