Question

I am using Django and trying to calculate the average client age, and for some reason this answer is escaping me. What I want to do is to loop through all clients in a group and get the mean delta of today and their dob.

Here is what the model looks like:

class Client (models.model):
  ...
  dob = models.DateField(
                         null = False
                        )

So that I am trying to do something like this:

def age(self,qrydtm=date.today())
  # here is a method (from funcs.py) that returns a list of dob for the group
  delta = 
  delta_m = ((qrydate.year - self.dob.year)*12)+(qrydate.month - self.dob.month)         
  years = delta_m // 12
  weeks = delta // 7
  months = (delta_m - (years*12))
  if (years > 0):
    return ('%s yr - %s mn' % (years,months))
  else:
    return ('%s wk' % (weeks))  

The method I am using, creates a list of dob like this [(datetime.date(1976, 8, 4),), (datetime.date(2005, 8, 8),), (datetime.date(1986, 10, 14),)]

Answer 1

This will get you the average age as a timedelta:

l = [datetime.date(1976, 8, 4), datetime.date(2005, 8, 8), ...] # values_list(flat=True)
today = datetime.date.today()
average_age = sum(map(lambda x: today-x, l), datetime.timedelta(0))/len(l)

Edit:

With l being potentielly large I avoided the second list:

from datetime import date, timedelta
l = [date(1976, 8, 4), date(2005, 8, 8), ...] # values_list(flat=True)
today = date.today()
average_age = sum((today - x for x in l), timedelta(0)) / len(l)