op=Expression(left, operator, right)

from peewee import Expression # the building block for expressions

def mod(lhs, rhs):
   return Expression(lhs, '%', rhs)

from peewee import *
db = SqliteDatabase('mydatabase.db')

class BaseModel(Model):
   class Meta:
      database = db

class Contacts(BaseModel):
   RollNo = IntegerField()
   Name = TextField()
   City = TextField()

db.create_tables([Contacts])

from peewee import Expression # the building block for expressions

def mod(lhs, rhs):
   return Expression(lhs,'%', rhs)
qry=Contacts.select().where (mod(Contacts.id,2)==0)
print (qry.sql())
for q in qry:
   print (q.id, q.Name, q.City)

('SELECT "t1"."id", "t1"."RollNo", "t1"."Name", "t1"."City" FROM "contacts" AS "t1" WHERE (("t1"."id" % ?) = ?)', [2, 0])

2  Amar Delhi
4  Leena Nasik
6  Hema Nagpur
8  John Delhi
10 Raja Nasik