Generate attachment on Odoo 11

attachment_odoo11_example.py

import base64
from odoo import models, fields, api

class SomeModel(models.Model):
    _name = 'some.model'

    field1 = fields.Char(string="Field 1")
    field2 = fields.Boolean(string="Field 2")

    @api.multi
    def action_generate_attachment(self):
        """ this method called from button action in view xml """
        # generate pdf from report, use report's id as reference
        REPORT_ID = 'some_report_id'
        pdf = self.env.ref(REPORT_ID).render_qweb_pdf(self.ids)
        # pdf result is a list
        b64_pdf = base64.b64encode(pdf[0])

        # save pdf as attachment
        ATTACHMENT_NAME = "My Attachment Name"
        return self.env['ir.attachment'].create({
            'name': ATTACHMENT_NAME,
            'type': 'binary',
            'datas': b64_pdf,
            'datas_fname': ATTACHMENT_NAME + '.pdf',
            'store_fname': ATTACHMENT_NAME,
            'res_model': self._name,
            'res_id': self.id,
            'mimetype': 'application/x-pdf'
        })