Question

I have a question in Django on how you can compare dates to solve some solutions. For example I have a datefield in my models.py Like below.

class Invoice(models.Model):
    payment_date = models.DateTimeField()

What I want to be able to do is ask if the is a way to compare a datetime.now with a DateTimeField. For example, if I had a list of payment dates and I wanted to compare with datetime now. Thhe payment_date’s that are late with their payments are shown in owing. Otherwise, it the value is zero.

Here is my views to show whats going on. I have tried so far but I get a 0 value for payment_date’s which are later than the payment date.

Edit here is my latest views. Funny thing is that I seem to be getting the owing = invoice_gross for all results – unlike before when I was getting all 0s. So it is still not working properly.

@login_required
def homepage(request):
    invoices_list = Invoice.objects.all()
    invoice_name = invoices_list[0].client_contract_number.client_number.name
    invoice_gross = invoices_list[0].invoice_gross
    payment_date = invoices_list[0].payment_date
    if payment_date <= datetime.now():
        owing = invoice_gross
        if payment_date > datetime.now():
            owing = 0
    return render_to_response(('index.html', locals()), {'invoices_list': invoices_list ,'invoice_name':invoice_name, 'invoice_gross':invoice_gross,'payment_date':payment_date,'owing':owing}, context_instance=RequestContext(request))

Oh and my table is basically doing something like this.

ID  Owing
1   100   (All the same value)
2   100
3   100
.   .
.   .
.   .

Answer 1

I think the problem is in the line

if datetime.now() == payment_date:

That will literally see if the payment_date is right now. I think you want to see if now is greater than or equal to the payment_date, in which case you should use

if datetime.now() >= payment_date:

You can also just filter the invoices when you query the database:

invoices_list = Invoice.objects.filter(payment_date__lte=datetime.now())

Update

Your code is wrong because you have mutually exclusive conditionals. Look:

if payment_date <= datetime.now():
    owing = invoice_gross
    if payment_date > datetime.now():
        owing = 0

That first checks to see if payment_date is before now. Then it sets owing to invoice_gross. Then, in the same conditional, it checks to see if payment_date is after now. But that can’t be! You are only in this block of code if payment_date is before now!

I think you have an indentation error, and want this instead:

if payment_date <= datetime.now():
    owing = invoice_gross
if payment_date > datetime.now():
    owing = 0

Which, of course, is the same as:

if payment_date <= datetime.now():
    owing = invoice_gross
else:
    owing = 0