Question

I have two lists like below.i am getting this from database

EmpID = Assign.objects.select_related().filter(pName=selProject).filter()
    .order_by('laEmpNum').values_list('laEmpNum', flat=True)

TotDur = Assign.objects.select_related().filter(pName=selProject).order_by('laEmpNum')
    .values_list('duration', flat=True)

EmpID = [u'1046', u'1046', u'1046', u'8008', u'8008', u'8011'] 

TotDur = [0.0, 2.0, 2.5, 0.0, 2.7, 1.2] 

If EmpIDs are same then corresponding values in TotDur should collect and add(sum).

ResOne = 0.0 + 2.0 + 2.5    i.e 4.5
ResTwo = 0.0+2.7            i.e 2.7
ResThr = 1.2                i.e 1.2

How to do this in Python.

Answer 1

If the elements are in order as you have shown in your example, you can use itertools.groupby

from itertools import groupby
from operator import itemgetter
[(k , sum(e for _,e in v)) for k,v in groupby(zip(EmpID, TotDur), itemgetter(0))]
[(u'1046', 4.5), (u'8008', 2.7), (u'8011', 1.2)]

infact you don’t need to create two separate list and zip it later

Emp_TotDur = Assign.objects.select_related().filter(pName=selProject).filter()
    .order_by('laEmpNum').values_list('laEmpNum', 'duration')

[(k , sum(e for _,e in v)) for k,v in groupby(Emp_TotDur, itemgetter(0))]