In odoo-9 we create functional fields and validate to function and set also set to default value of Unit of Measure Categories(UOM) in selected form.

Use this step show in given below

Step1- First create fields in your own module in .py file, show in given below

class nursery(models.Model):

 def default_duration_unity(self, cr, uid, context=None):

        """
        Returns the 1st UoM present into the Duration category.
        """
        unity1 = self.pool['product.uom'].search(cr, uid, [])[16]
        unity = self.pool['product.uom'].browse(cr, uid, unity1)
        if not unity:
            _logger.warning("It seems that there isn't a reference unity in the 'Duration' UoM category. "
                            "Please check that the category exists, and there's a reference unity.")

        return unity.id if unity else False

    _name = 'nursery'
   _columns = {
    
Untitled 1
   'rent_duration_unity' : fields.many2one('product.uom',  string='Unity',
required=True, 
    
     }

  _defaults = {
                 'rent_duration_unity' : default_duration_unity,
                 }
nursery()

Step2- Then we create view in .xml file in your own module show in given below

<?xml version="1.0"?>
<openerp>
<data>

<record id="view_nursery_form77" model="ir.ui.view">
            <field name="name">view.feedback.form</field>
            <field name="model">feedback</field>
            <field name="arch" type="xml">
                <form string="Feedback">
                    <group>
                        <field name="rent_duration_unity"/>
                    </group>
                </form>
            </field>
        </record>

<record id="action_nursery33" model="ir.actions.act_window">
            <field name="name">Feedback</field>
            <field name="type">ir.actions.act_window</field>
            <field name="res_model">feedback</field>
            <field name="view_mode">tree,form</field>
        </record>


    <menuitem name="nursery" id="menu_student"/>
    <menuitem name="nursery" id="menu_nursery_item" parent="menu_student" action="action_nursery"/>
   <menuitem name="nursery create" id="menu_nursery_item" parent="menu_student" action="action_nursery33"/>

</data>
</openerp>