Question

I am creating a list from some of the model data but I am not doing it correctly, it works but when I refresh the page in the broswer reportResults just gets added to. I hoped it would get garbage collected between requests but obviously I am doing something wrong, any ideas anyone??

Thanks,
Ewan

reportResults = []   #the list that doesn't get collected
def addReportResult(fix,description):  
    fix.description = description
    reportResults.append(fix)

def unitHistory(request,unitid, syear, smonth, sday, shour, fyear, fmonth, fday, fhour, type=None):
   waypoints = Fixes.objects.filter(name=(unitid))
    waypoints = waypoints.filter(gpstime__range=(awareStartTime, awareEndTime)).order_by('gpstime')[:1000]
    if waypoints:
        for index in range(len(waypoints)): 
...do stuff here selecting some waypoints and generating "description" text
                    addReportResult(waypointsindex,description) ##append the list with this, adding a text description

    return render_to_response('unitHistory.html', {'fixes': reportResults})   

Answer 1

Just so you’re aware of the life cycle of requests, mod_wsgi will keep a process open to service multiple requests. That process gets recycled every so often but it is definitely not bound to a single request as you’ve assumed.

That means you need a local list. I would suggest moving the addReportResult function contents directly in-line, but that’s not a great idea if it needs to be reusable or if the function is too long. Instead I’d make that function return the item, and you can collect the results locally.

def create_report(fix, description): # I've changed the name to snake_casing
    fix.description = description
    return fix

def unit_history(request,unitid, syear, smonth, sday, shour, fyear, fmonth, fday, fhour, type=None):
    reports = []
    waypoints = Fixes.objects.filter(name=(unitid))
    waypoints = waypoints.filter(gpstime__range=(awareStartTime, awareEndTime)).order_by('gpstime')[:1000]
    if waypoints:
        for index in range(len(waypoints)): 
            report = create_report(waypointsindex, description)
            reports.append(report)
    return render_to_response('unitHistory.html', {'fixes': reportResults})