$ ls -1 /var/lib/apt/lists/
archive.canonical.com_ubuntu_dists_precise_partner_binary-i386_Packages
archive.canonical.com_ubuntu_dists_precise_partner_source_Sources
archive.canonical.com_ubuntu_dists_precise_Release
archive.canonical.com_ubuntu_dists_precise_Release.gpg
gb.archive.ubuntu.com_ubuntu_dists_precise_main_binary-i386_Packages
gb.archive.ubuntu.com_ubuntu_dists_precise_main_i18n_Translation-en%5fGB
gb.archive.ubuntu.com_ubuntu_dists_precise_main_source_Sources
gb.archive.ubuntu.com_ubuntu_dists_precise_multiverse_binary-i386_Packages
gb.archive.ubuntu.com_ubuntu_dists_precise_multiverse_i18n_Translation-en%5fGB
gb.archive.ubuntu.com_ubuntu_dists_precise_multiverse_source_Sources
gb.archive.ubuntu.com_ubuntu_dists_precise_Release
gb.archive.ubuntu.com_ubuntu_dists_precise_Release.gpg
gb.archive.ubuntu.com_ubuntu_dists_precise_restricted_binary-i386_Packages
gb.archive.ubuntu.com_ubuntu_dists_precise_restricted_i18n_Translation-en%5fGB
gb.archive.ubuntu.com_ubuntu_dists_precise_restricted_source_Sources
gb.archive.ubuntu.com_ubuntu_dists_precise_universe_binary-i386_Packages
gb.archive.ubuntu.com_ubuntu_dists_precise_universe_i18n_Translation-en%5fGB
gb.archive.ubuntu.com_ubuntu_dists_precise_universe_source_Sources
gb.archive.ubuntu.com_ubuntu_dists_precise-updates_main_binary-i386_Packages
gb.archive.ubuntu.com_ubuntu_dists_precise-updates_main_i18n_Translation-en%5fGB
gb.archive.ubuntu.com_ubuntu_dists_precise-updates_main_source_Sources
gb.archive.ubuntu.com_ubuntu_dists_precise-updates_multiverse_binary-i386_Packages
gb.archive.ubuntu.com_ubuntu_dists_precise-updates_multiverse_i18n_Translation-en%5fGB
gb.archive.ubuntu.com_ubuntu_dists_precise-updates_multiverse_source_Sources
gb.archive.ubuntu.com_ubuntu_dists_precise-updates_Release
gb.archive.ubuntu.com_ubuntu_dists_precise-updates_Release.gpg
gb.archive.ubuntu.com_ubuntu_dists_precise-updates_restricted_binary-i386_Packages
gb.archive.ubuntu.com_ubuntu_dists_precise-updates_restricted_i18n_Translation-en%5fGB
gb.archive.ubuntu.com_ubuntu_dists_precise-updates_restricted_source_Sources
gb.archive.ubuntu.com_ubuntu_dists_precise-updates_universe_binary-i386_Packages
gb.archive.ubuntu.com_ubuntu_dists_precise-updates_universe_i18n_Translation-en%5fGB
gb.archive.ubuntu.com_ubuntu_dists_precise-updates_universe_source_Sources
lock
partial/
security.ubuntu.com_ubuntu_dists_precise-security_main_binary-i386_Packages
security.ubuntu.com_ubuntu_dists_precise-security_main_source_Sources
security.ubuntu.com_ubuntu_dists_precise-security_multiverse_binary-i386_Packages
security.ubuntu.com_ubuntu_dists_precise-security_multiverse_source_Sources
security.ubuntu.com_ubuntu_dists_precise-security_Release
security.ubuntu.com_ubuntu_dists_precise-security_Release.gpg
security.ubuntu.com_ubuntu_dists_precise-security_restricted_binary-i386_Packages
security.ubuntu.com_ubuntu_dists_precise-security_restricted_source_Sources
security.ubuntu.com_ubuntu_dists_precise-security_universe_binary-i386_Packages
security.ubuntu.com_ubuntu_dists_precise-security_universe_source_Sources
$

$ dpkg -s python
Package: python
Status: install ok installed
Priority: important
Section: python
Installed-Size: 640
Maintainer: Ubuntu Developers <email address hidden>
Architecture: all
Source: python-defaults
Version: 2.6.5-0ubuntu1
Replaces: python-base, python-xmlbase, python2.3 (<= 2.3.2-6)
Provides: python-ctypes, python-email, python-plistlib, python-wsgiref, python-xmlbase
Depends: python2.6 (>= 2.6.5), python-minimal (= 2.6.5-0ubuntu1)
Suggests: python-doc (>= 2.6.5-0ubuntu1), python-tk (>= 2.6.5-0ubuntu1), python-profiler (>= 2.6.5-0ubuntu1)
Conflicts: libboost-dbg (<< 1.34.1-15ubuntu3), libboost-python-dev (<< 1.34.1-15ubuntu3), libboost-python1.35-dev (<< 1.35.0-8ubuntu5), libboost1.35-dbg (<< 1.35.0-8ubuntu5), pitivi (<< 0.11.3-1ubuntu1), python-aubio (<< 0.3.2-2ubuntu3), python-base, python-bz2, python-central (<< 0.5.5), python-csv, python-freevo (<< 1.8.1-3ubuntu3), python-xmlbase, python2.1 (<= 2.1.2), python2.3 (<< 2.3.5-14), qmtest (<< 2.4-5ubuntu1), ufw (<< 0.27~r416)
Description: An interactive high-level object-oriented language (default version)
 Python, the high-level, interactive object oriented language,
 includes an extensive class library with lots of goodies for
 network programming, system administration, sounds and graphics.
 .
 This package is a dependency package, which depends on Debian's default
 Python version (currently v2.6).
Original-Maintainer: Matthias Klose <email address hidden>
$

$ apt-cache policy python
python:
  Installed: 2.6.5-0ubuntu1
  Candidate: 2.7.3-0ubuntu2
  Version table:
     2.7.3-0ubuntu2 0
        500 http://gb.archive.ubuntu.com/ubuntu/ precise/main Packages
 *** 2.6.5-0ubuntu1 0
        100 /var/lib/dpkg/status
$