Django: empty date string should return all - mysql

Question

So, I have a date from input field, and date to input field. When I pass in the date range from and to it works fine. But when I try to leave one or both blank, to get all the items, or partial items, it gives ValueError: Cannot use None as a query value or format error when I try to make the default empty string.
def report(self, request):
date_from = query['date_from'] if query['date_from'] else None
date_to = query['date_to'] if query['date_to'] else None
queryset = Client.objects.filter(
client_code__in=clients,
account__note__creation_time__gte=date_from,
account__note__creation_time__lte=date_to,
)
To give a better context, if I leave both field empty i should get all items from beginning to now, if I fill in date from field but leave date to field empty, I should get all item from date from till now. If I have date to field buy empty date from field, I should get items from beginning till date to.
Got lazy and found a solution that works but not very happy with it. If someone finds something better feel free to share.
query = Q()
if clients:
clients = clients.split(',')
query &= Q(client_code__in=clients)
if date_from:
query &= Q(account__note__creation_time__gte=date_from)
if date_to:
query &= Q(account__note__creation_time__lte=date_to)
Client.objects.filter(query)

Answer 1

If you put a filter on the queryset you have to supply valid values for that filter.. Django can't guess that you actually don't want the filter after all...
But there are ways to make it a little nicer looking, eg:
qs = Client.objects.all()
if date_from:
qs = qs.filter(account__note__creation_time__gte=date_from)
if date_to:
qs = qs.filter(account__note__creation_time__lte=date_to)
# etc etc for all your AND queries.
# but for OR type queries you need to use Q objects.
When you create a queryset, as I did using Client.objects.all, it doesn't actually go to the database and get the objects right away. So you can then modify that queryset by adding additional filters onto it to limit your results. You can use all the different queryset methods.. eg order_by(), fetch_related() etc.. until the queryset is how you want it. It won't actually execute any SQL until you try to read the objects by iterating over the queryset, eg:
# now it will go to the database and get the objects based on your filters.
for instance in qs:
print instance
So you see, in this case, where all your filters are narrowing the search (they are all AND'ed together), there's no need to use Q() and that makes for less typing and clearer code. But if you are doing a query where you are using OR logic or where you are perhaps applying the same query to multiple querysets, then you do need to use the Q class to form that query.