Re: What's wrong with this code?

From	Thomas Rachel <nutznetz-0c1b6768-bfa9-48d5-a470-7603bd3aa915@spamschutz.glglgl.de>
Newsgroups	comp.lang.python
Subject	Re: What's wrong with this code?
Date	2012-07-24 10:34 +0200
Organization	A newly installed InterNetNews server
Message-ID	<julmmp$s13$1@r03.glglgl.gl> (permalink)
References	<mailman.2478.1343055006.4697.python-list@python.org>

Show all headers | View raw

Am 23.07.2012 16:50 schrieb Stone Li:
> I'm totally confused by this code:
>
> Code:
>
>     a = None
>     b = None
>     c = None
>     d = None
>     x = [[a,b],
>           [c,d]]
>     e,f = x[1]
>     print e,f
>     c = 1
>     d = 2
>     print e,f
>     e = 1
>     f = 2
>     print c,d
>
> Output:
>
>     None None
>     None None
>     1 2
>
>
> I'm expecting the code as:
>
>     None None
>     1 2
>     1 2
>
>
> What's wrong?

Your expectation :-)

With c = 1 and d = 2 you do not change the respective objects, but you 
assign other objects to the same names.

The old content is still contained in x[1].

If you would only modify these objects (not possible as ints are 
immutable), you would notice the changes here and there.


Thomas

Back to comp.lang.python | Previous | Next — Previous in thread | Find similar | Unroll thread

Thread

What's wrong with this code? Stone Li <viewfromoffice@gmail.com> - 2012-07-23 22:50 +0800
  Re: What's wrong with this code? Andrew Cooper <amc96@cam.ac.uk> - 2012-07-24 02:19 +0100
    Re: What's wrong with this code? Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-07-24 07:23 +0100
    Re: What's wrong with this code? Devin Jeanpierre <jeanpierreda@gmail.com> - 2012-07-24 03:38 -0400
    Re: What's wrong with this code? Ian Kelly <ian.g.kelly@gmail.com> - 2012-07-24 02:26 -0600
  Re: What's wrong with this code? Ulrich Eckhardt <ulrich.eckhardt@dominolaser.com> - 2012-07-24 09:47 +0200
    Re: What's wrong with this code? Chris Angelico <rosuav@gmail.com> - 2012-07-24 18:24 +1000
      Re: What's wrong with this code? Ulrich Eckhardt <ulrich.eckhardt@dominolaser.com> - 2012-07-24 12:05 +0200
    Re: What's wrong with this code? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-07-24 08:26 +0000
    Re: What's wrong with this code? Thomas Rachel <nutznetz-0c1b6768-bfa9-48d5-a470-7603bd3aa915@spamschutz.glglgl.de> - 2012-07-24 11:34 +0200
  Re: What's wrong with this code? Thomas Rachel <nutznetz-0c1b6768-bfa9-48d5-a470-7603bd3aa915@spamschutz.glglgl.de> - 2012-07-24 10:34 +0200

csiph-web