get_chi_So.py

import calendar
from datetime import datetime as date

def get_date_range(self, month, year):
    last_day_of_month = calendar.monthrange(year, month)[1]
    begin_date = date(year, month, 1).strftime('%Y-%m-%d')
    end_date = date(year, month, last_day_of_month).strftime('%Y-%m-%d')
    return begin_date, end_date
  
# -----------------------------------------
# Code
# -----------------------------------------
begin_date, end_date = self.get_date_range(month, year)
figure = self.env['working.rate'].search([
    ('employee_code', '=', self.employee_code),
    ('date', '>=', begin_date),
    ('date', '<=', end_date),
]).x_value