@p.n1@gmx.net answered is useful to implement the Many2one field.

But in the case of Selection field, Try this

your_field = fields.Selection([('sale', 'Sales'), ('purchase', 'Purchases'), ('none', 'None')])

 <select class="form-control" name="your_field">
       <option t-attf-value="'sale'">Sales</option>
       <option t-attf-value="'purchase'">Purchases</option>
       <option t-attf-value="'none'">None</option>
 </select>

Thanks 

Hi,

By doing following you can add a selection field into the frontend.

<select name="your_field" id="your_field_id"

        style="width:290px; height:45px"

        class="advanced-select">

    <t t-foreach='your_field' t-as="field" >

        <option t-esc='field.name' t-att-value="field.id"/>

    </t>

</select>

Regards

@ Ajay

<select class="form-control" name="category">
     <t t-foreach="categories" t-as="category">
          <option t-attf-value="#{category.id}" t-att-selected="WHATEVER_CATEGORY_ID_YOU_WANT_TO_HAVE_SELECTED"><t t-esc="category.name"/></option>
     </t>
 </select>

Just add the t-att-selected attribute and give it the value you want to have selected from your otions

@Shameem 

Your answer is working, but how to populate the field with the already selected value.

Please help me with this.