Django try..除了用n引发的ValueError

Question

我试图允许用户通过包含try:...except ValueError:来选择性地提交数据，但是即使包含了所有输入值，except也会被触发。在

def sByInfo(request):
    print "\n \n NEW CALL"

    ranked = Ranked.objects.all()
    unranked = Unranked.objects.all()

    ranked_matches = [] # List for ranked institution matches
    unranked_matches = [] # List for unranked institution matches

    try:
        gpa = request.GET['gpa']
        gpa = float(gpa)
        print gpa
        pcat = request.GET['pcat']
        pcat = int(pcat)
        print pcat

        try:
            city = request.GET['city']
            state = request.GET['state']
            print "{}, {}".format(city, state)

            position = getPos(city, state)
            lati = Decimal(position['lat'])
            loni = Decimal(position['lon'])

            print "\n RANKED"
            for x in ranked:
                print x.name
                average_gpa = (x.gpa_expected + x.gpa_overall) / 2
                print average_gpa
                if gpa >= average_gpa:
                    print "GPA good"
                    if ranked_matches.index(x):
                        print "School already added"
                    else:
                        ranked_matches.append(x)
                        print "School added"
                else:
                    print "GPA too low"

                if pcat >= x.min_pcat:
                    if ranked_matches.index(x):
                        print "School already added"
                    else:
                        ranked_matches.append(x)
                else:
                    print "PCAT too low"

                lat = Decimal(x.lat)
                lon = Decimal(x.lon)
                difference = posDifference(lati, loni, lat, lon)
                print "Distance is {} miles".format(difference)

                if difference <= 150:
                    if ranked_matches.index(x):
                        print "School already added"
                    else:
                        ranked_matches.append(x)
                else:
                    print "School out of range"

            print "\n UNRANKED"
            for y in unranked:
                print y.name
                average_gpa = (y.gpa_expected + y.gpa_overall) / 2
                if gpa >= average_gpa:
                    if unranked_matches.index(y):
                        print "School already added"
                    else:
                        unranked_matches.append(y)
                else:
                    print "GPA too low"

                if pcat >= y.min_pcat:
                    if unranked_matches.index(y):
                        print "School already added"
                    else:
                        unranked_matches.append(y)
                else:
                    print "PCAT too low"

                lat = Decimal(y.lat)
                lon = Decimal(y.lon)
                difference = posDifference(lati, loni, lat, lon)
                print "Distance is {} miles".format(difference)

                if difference <= 150:
                    if unranked_matches.index(y):
                        print "School already added"
                    else:
                        unranked_matches.append(y)
                else:
                    print "School out of range"



        except ValueError: ## City or State was not submitted
            print "City or state missing"

            try:
                state = request.GET['state']
            except ValueError:
                print "City and state missing"

    except ValueError:
        return render('You must enter both GPA & PCAT scores')


    return render_to_response('results.html', {'ranked_matches' : ranked_matches, 'unranked_matches' : unranked_matches}, context_instance = RequestContext(request))

第一个for循环通过一次迭代，没有明显的失败，然后引发第一个嵌套异常，返回“City or state missing”消息。我不明白为什么在提交所有值时会引发此异常。在

我相信这个问题一定是在这个if声明中的某个地方

^{pr2}$

感谢所有的帮助，谢谢。在

Answer 1

我认为ValueError不够健壮

如果数据类型不正确

int('test')

它引发一个ValueError，因此它不是检查字段是否存在的足够方法。在

更健壮的方法是使用djangos built in Forms。它允许您指定数据类型和必需的字段，django将负责为您进行验证。在