More about variables
culliton at clark.net
Fri Apr 7 00:52:57 CEST 2000
In article <meh9-158D1A.14240006042000 at news.cit.cornell.edu>,
Matthew Hirsch <meh9 at cornell.edu> wrote:
>Why create named variables?
>I always thought that having 20 lists saved more space than having one
>list of 20 lists. Maybe I'm wrong.
You are, but it's an honest mistake since Python is different from
many common languages here. Every Python "variable" is really a
dictionary entry, which means a string for the name, the data, and a
pair of references to them. So a list of lists saves you the string,
one of the references, and lets you deal with the data more uniformly
making it a win all the way around.
You should probably dig through some of the online docs and tutorials
to get a better handle on how Python represents things internally and
how "variable" names and assignment really work. Rather than names
being tightly fixed to a particular area of memory they are loosely
and indirectly associated with data objects. An object can have many
different names during it's lifetime (sequentially or in parallel),
and a name can (sequentially) refer to many different objects. There
are really no such thing as variables in python only objects and
their (more or less temporary) names.
For example: (the id() function essentially returns the address of the
object refered too.)
Python 1.5.2 (#1, Sep 17 1999, 20:15:36) [GCC egcs-2.91.66 19990314/Linux (egcs- on linux-i386
Copyright 1991-1995 Stichting Mathematisch Centrum, Amsterdam
>>> x = 1
>>> y = x
>>> z = y
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