Django - How to add a custom ID column to identify my objects? -

(first of sorry bad english, hope can understand me)

well have add custom id objects of 1 of models, custom id going have letter p or l if related object have 1 or other attribute. if employee has "planta permantente" or "planta contratada" attribute custom id start p , if have "locacion de servicio" attribute start l. both need have correlative numbers. if have p1 when add new certificate employee "locacion de servicio" custom id have "l1" , next p "p2"

how can this??

this part of employee model

contract_types = (     (1, ("planta permanente")),     (2, ("planta contratada")),     (3, ("locación de servicio")), )  class employee(models.model):      cuil = models.charfield(             unique=true,             max_length=11,             verbose_name=_('cuil'),         )     name = models.charfield(             max_length=50,             verbose_name=_('first name'),         )     middle_name = models.charfield(             blank=true,             max_length=50,             verbose_name=_('middle name'),         )     last_name = models.charfield(             max_length=100,             verbose_name=_('last name'),         )     have_children = models.booleanfield(             default=false)     contract = models.integerfield(             choices=contract_types,             verbose_name=_('contract'),         ) 

and part of certificate model

class certificate(models.model):     employee = models.foreignkey(             employee,             verbose_name=_('employee'),         )     place = models.integerfield(             choices=accident_place,             default=1,             verbose_name=_('place')         )     detail = models.charfield(             max_length=255,             verbose_name=_('detail'),         )     clinic = models.foreignkey(             clinic,             verbose_name=_('clinic'),         ) 

well thats need do, if employee have contract type 1 or 2 identify p1 p2 p3...p100...pn , if 3 same l letter.

any idea?

(thanks much)

have read approach in docs: https://docs.djangoproject.com/en/1.9/ref/models/instances/#explicitly-specifying-auto-primary-key-values ?

would if manually specified custom id (a simple 'if' do?) have p1,l1 or p2 in front , save shown in django docs link above? make sure numbers consecuitive (i assume want have like: l101, p102, p103, p204 etc.?) combine custom id auto-primary key, right?

so model have auto-generated id , additionally custom id first 2 letters specified wich , following digits copy auto-generated primary-key.

hope helps!