Unable to see os.environ['COLUMNS']

[Tim Chase]

Not sure what's going on here and hoping for some insight:

   tim at rubbish:~$ echo $COLUMNS
   129
   tim at rubbish:~$ python2.5
   Python 2.5.2 (r252:60911, May 28 2008, 08:35:32)
   [GCC 4.2.4 (Debian 4.2.4-1)] on linux2
   Type "help", "copyright", "credits" or "license" for more 
information.
   >>> import os
   >>> os.environ.get('COLUMNS')
   >>>  'COLUMNS' in os.environ
   False

I can coerce it by using

   tim at rubbish:~$ COLUMNS=$COLUMNS python2.5
   Python 2.5.2 (r252:60911, May 28 2008, 08:35:32)
    [GCC 4.2.4 (Debian 4.2.4-1)] on linux2
   Type "help", "copyright", "credits" or "license" for more 
information.
   >>> import os
   >>> 'COLUMNS' in os.environ
   True

However, this seems hokey to me.

FWIW, this is in Bash on Debian.

What's the best way to read what seems to be a pseudo-environment 
variable?

-tkc