list index out of range django

Question

Can someone explain me why am I getting back list index out of range, it occur in two places in my view, first one is in context_data = self.get_context_data(user_id, month, year, form=form) and context['month'] = calendar.month_name[month], so can someone explain me what is happening in my code. Here is a full Traceback

my view:

import calendar
import datetime

from django.contrib import messages
from django.contrib.auth.models import User
from django.core.urlresolvers import reverse
from django.http import HttpResponseForbidden
from django.shortcuts import redirect, get_object_or_404
from django.views.generic.edit import FormView

from .helpers.user_util import get_user_full_name_or_user_name
from models import Rate
from statistics.forms import CommissionsMonthSelectionForm
from statistics.services import ManagerCommissionsProjectsCalculation, CommissionsAccessService


class UserSalesCommissionsView(FormView):
    template_name = "statistics/user_sales_commissions.html"
    form_class = CommissionsMonthSelectionForm
    currency = Rate.EUR

    def get(self, request, *args, **kwargs):
        user_id = self.kwargs['user_id']
        requesting_user = request.user
        if CommissionsAccessService.can_view_commissions_page(requesting_user, user_id):
            month = int(self.request.GET.get('month', datetime.datetime.now().month))
            year = int(self.request.GET.get('year', datetime.datetime.now().year))
            form = CommissionsMonthSelectionForm(initial={'year': year, 'month': month})
            context_data = self.get_context_data(user_id, month, year, form=form)
            return self.render_to_response(context_data)
        else:
            return HttpResponseForbidden('Access denied')

    def post(self, request, *args, **kwargs):
        user_id = self.kwargs['user_id']
        requesting_user = self.request.user

        if CommissionsAccessService.can_view_commissions_page(requesting_user, user_id):
            form_class = self.get_form_class()
            form = self.get_form(form_class)
            if form.is_valid():
                return self.form_valid(form, user_id)
            else:
                return self.form_invalid(form)
        else:
            return HttpResponseForbidden('Access denied')

    def form_valid(self, form, user_id=None):
        year = form.cleaned_data['year']
        month = form.cleaned_data['month']
        return redirect(self.get_success_url(user_id, month, year))

    def form_invalid(self, form):
        messages.add_message(self.request, messages.ERROR,
                             "Invalid data. Please check fields.")
        return self.render_to_response(
            self.get_context_data(form=form)
        )

    def get_success_url(self,
                        user_id=None,
                        year=datetime.datetime.now().year,
                        month=datetime.datetime.now().month):
        return reverse("vinclucms_statistics:manager_commissions_statistics", user_id) + \
               "?month=" + str(month) + "&year=" + str(year)

    def get_context_data(self,
                         user_id=None,
                         year=datetime.datetime.now().year,
                         month=datetime.datetime.now().month,
                         **kwargs):
        context = super(UserSalesCommissionsView, self).get_context_data(**kwargs)
        context['user_name'] = get_user_full_name_or_user_name(get_object_or_404(User, pk=user_id))
        context['can_view'] = True
        context['currency'] = self.currency
        context['month'] = calendar.month_name[month]
        context['year'] = year

        context['commissions'] = ManagerCommissionsProjectsCalculation.get_project_list(
            self.currency, year, month, user_id)
        return context

views urls:

url(r'^statistics/commissions/sales/(?P<user_id>[^/]+?)/$', login_required(views.UserSalesCommissionsView.as_view()), name='user_sales_commissions')

Answer 1

month = datetime.datetime.now().month # IF Current month is April then month==4

calendar.month_name[month]

An array that represents the months of the year in the current locale. This follows normal convention of January being month number 1, so it has a length of 13 and month_name[0] is the empty string.

here : calendar.month_name[month] check what is the value of month it should be 4 because current month is April.

So you are passing String where it is required a datetime object.

Answer 2

Here's get_context_data's definition:

def get_context_data(self,
                     user_id=None,
                     year=datetime.datetime.now().year,
                     month=datetime.datetime.now().month,
                     **kwargs):

And here's how it's called:

context_data = self.get_context_data(user_id, month, year, form=form)

so the 2 keyword arguments (year and month) are reversed yielding to something like calendar.month_name[2017] which would spit the Indexerror.

You should pass the arguments in the right order, or when dealing with keyword arguments, always specify their name:

context_data = self.get_context_data(user_id=user_id, month=month, year=year, form=form)

and that way their order would not be important any more.

Might also want to check PEP 3102.