in your py file

from openerp import models, fields, api, _
from datetime import datetime
AVAILABLE_PRIORITIES = [
    ('0', 'Very Low'),
    ('1', 'Low'),
    ('2', 'Normal'),
    ('3', 'High'),
    ('4', 'Very High')]

class Attend(models.Model):
    _name="permission.details"

    
    set_priority=fields.Selection(AVAILABLE_PRIORITIES, select=True)

in ur xml file

<field name="set_priority" widget="priority"></field>