On Sun, 2006-06-11 at 22:14 -0400, Kermit Rose wrote: > Message: 1 > Date: Sun, 11 Jun 2006 06:58:39 -0400 > From: Kent Johnson <[EMAIL PROTECTED]> > Subject: Re: [Tutor] buggy bug in my program > Cc: tutor@python.org > > Assignment in Python is not a copy, it is a name binding. Assignment > creates a name for an object. If you assign the same object to two > names, they both are bound to the same thing. If the object is mutable, > like a list, changes to the object will be seen regardless of which name > you use to refer to it. > > ****** > > I feel a little bit better now that I know that there is a reason for what > my > program did. > > However, I still don't have any idea how to copy values from one cell in > an array to the adjacent cell in the same array. > > I looked at the reference , > > http://www.effbot.org/zone/python-objects.htm > > that you gave, > > but did not gleam any hint from it how to copy values from one place in an > array to another place within the same array. > > It must be possible, for otherwise, you could not sort an array. > > > It is quite remarkable that my not knowing that > > assignment is not a copy > > gave me no difficulties before now. The basic python objects: numbers, strings, and tuples are immutable and can not be changed (mutated). a = b = 3 b = 4 # binds b to a different object with value 4 # the object with value 3 is unchanged print a 3
Container objects such as lists and dictionaries can be changed in place. >>> a = b = [1,2,3] >>> b.append(4) # changes (mutates) b >>> print a [1, 2, 3, 4] >>> b[2] = b[3] # positions 2 and 3 reference the same object >>> print b [1, 2, 4, 4] >>> print a [1, 2, 4, 4] > > > > Kermit < [EMAIL PROTECTED] > > > > > _______________________________________________ > Tutor maillist - Tutor@python.org > http://mail.python.org/mailman/listinfo/tutor -- Lloyd Kvam Venix Corp _______________________________________________ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
