<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def calc_list(request, id=None):
 # view associated to the endpoints /v1/calc/list and /v1/calc/:id/status """ Get a list of calculations and report their id, status, calculation_mode, is_running, description, and a url where more detailed information can be accessed. This is called several times by the Javascript. Responses are in JSON. """

    base_url = _get_base_url(request)
    calc_data = logs.dbcmd('get_calcs', request.GET,
                           utils.get_valid_users(request),
                           utils.get_acl_on(request), id)

    response_data = []
    username = psutil.Process(os.getpid()).username()
    for (hc_id, owner, status, calculation_mode, is_running, desc, pid,
         parent_id, size_mb) in calc_data:
        url = urlparse.urljoin(base_url, 'v1/calc/%d' % hc_id)
        abortable = False
        if is_running:
            try:
                if psutil.Process(pid).username() == username:
                    abortable = True
            except psutil.NoSuchProcess:
                pass
        response_data.append(
            dict(id=hc_id, owner=owner,
                 calculation_mode=calculation_mode, status=status,
                 is_running=bool(is_running), description=desc, url=url,
                 parent_id=parent_id, abortable=abortable, size_mb=size_mb))

    # if id is specified the related dictionary is returned instead the list
    if id is not None:
        [response_data] = response_data

    return HttpResponse(content=json.dumps(response_data),
                        content_type=JSON)