class Form(forms.Form):
    reports = forms.ModelChoiceField(queryset = None)
    def __init__(self,year,*args,**kwargs):
        super().__init__(*args,**kwargs)
        self.fields["reports"].queryset = Report.objects.filter(year = year)


def reports(request):
    years = Report.objects.values_list("year",flat = True).distinct()
    forms = []
    if request.method == "GET":
        for year in years:
            forms.append(Form(year))
        return render(request, "app/reports.html",{"forms":forms})
    if request.method == "POST":
        year =request.POST.get("reports")
        form = Form(year,request.POST)
        if form.is_valid():
            report = form.cleaned_data["reports"]
            return redirect(report.get_absolute_url())
        return render(request, "app/reports.html",{"form":form})