I'm practiced Python+Django edited Web， followed sample trying to export from db data into front Web and I want download CSV file. Here is my whole function. Its download a file, but it shows the for the title and not any data out.

Thanks all.

Views： sid search funtion

def search_by_sid(request,pk=1):
    sdepartments = Department.objects.all()
    cdepartments = CDepartment.objects.all()
    ssid = CourseData.objects.all()
    if request.method == "POST":
        sid = request.POST.get("sid").strip()
    if "," in sid:
        course = CourseData.objects.filter(sid="NA")
        sids = sid.split(",")
        for n in sids:
            courses = CourseData.objects.filter(sid = n.strip())
            course =course | courses
    else:    
        course = CourseData.objects.filter(sid=sid).order_by("teacher")
    num = len(course)        
    return render(request, "list.html")
return redirect("/")

donwload file function：

def down_file(request):
    sdepartments = Department.objects.all()
    cdepartments = CDepartment.objects.all()
    ssid = CourseData.objects.all()

if request.method == "POST":
    sids = request.POST.get("sid")
dfs = CourseData.objects.filter(sid__in=['sid']).values_list("sid","name","phone","email","sdept")
response = HttpResponse(content_type="text/csv")
response.write(codecs.BOM_UTF8)
response['Content-Disposition'] = 'attachment; filename = "Report.csv"'
writer = csv.writer(response)
print(writer)
writer.writerow(["sid","name","phone","email","sdept"])
for sop in dfs:
    writer.writerow(sop)
return response

Templates： button function

<form id="sid" action="/bysid/" method="post">
{% csrf_token %}
Search：<input name="sid" size="50" placeholder="Search">
<input type="submit" value="Go Search">
<input id="btnType" type="hidden" value="Search">
<button type="button" id="down_file" >Download Files</button>
</form>

js funtion：

$(document).ready(function(){
    $("#down_file").click(function(){
        $("#btnType").val('accpeted'); <!--Why Null ?!-->
        $("#sid").submit();       
    });
 });