I have two datefields fields in a Django model, start_date and end_date. I want to calculate and store the total number of days between the two, which will be used alongside a daily fee to return total cost.
models.py
class Booking(models.Model):
"""Stores the bookings, for example when it was made, the booking date, and the car ID."""
# Unique ID for this booking.
start_date = models.DateField(default=timezone.now)
end_date = models.DateField(null=True)
Most answers recommend extracting the days function (using start_date.day) but that doesn’t work. If a booking starts on November 30, and ends on December 2, the function will return 28 days because it subtracts the integers alone.
Using simple addition and subtraction:
duration = end_date - start_date
returns an error:
TypeError: Unsupported Operand type(s) for -: ‘DateField’ and ‘DateField’
I’ve tried using a function nested within the model, which subtracts each day from end_date until it reaches start_date:
def get_total_days(self):
"""Computes total number of days car will be rented from with a basic While loop."""
# Create separate instances of start and end day so as not to tamper with db values.
start_day = self.start_date
end_day = self.end_date
days = 0
while end_day > start_day:
days += 1
end_day -= 1
return days
But that raises the error:
Exception Value: unsupported operand type(s) for -=: ‘datetime.date’ and ‘int’
Can you help with this?
>Solution :
Add a method or property that subtracts the dates of an instance:
@property
def duration(self):
return (self.end_date - self.start_date).days