What are virtual packages?

[Colin Law]

On 9 September 2014 03:37, Robert Heller <heller at deepsoft.com> wrote:
> At Mon, 08 Sep 2014 20:25:03 -0500 "Ubuntu user technical support,  not for general discussions" <ubuntu-users at lists.ubuntu.com> wrote:
>
>>
>> Utunbu 12.04 & libreoffice 3.5..
>>
>> I am trying to run some example libreoffice python scripts and getting
>> errors.  Google suggests that one possible reason is that
>> libreoffice-script-provider-python is not installed.  It is not listed
>> in Synaptic.  This page [1] says that it is a virtual package provided
>> by python-uno.  Does this mean it is "built in"?
>
> A 'virtual package' is a package that does not install any files itself, but
> instead is dependent on some related 'set' of packages.

However that package does not seem to be available in  12.04 (it is in
14.04).  To check the availability of a package one can run, in a
terminal
 apt-cache policy  package-name
on 12.04 the result is
$  apt-cache policy  libreoffice-script-provider-python
libreoffice-script-provider-python:
  Installed: (none)
  Candidate: (none)
showing it is not installed and there is not a candidate version that
could be installed.

Colin