with db.atomic() as transaction:
   try:
      User.create(name='Amar', age=20)
      transaction.commit()
   except DatabaseError:
      transaction.rollback()

@db.atomic()
def create_user(nm,n):
   return User.create(name=nm, age=n)

create_user('Amar', 20)

with db.atomic() as txn1:
   User.create('name'='Amar', age=20)

   with db.atomic() as txn2:
      User.get(name='Amar')