title: How to update/ delete a key from a context in Odoo 10?
body: <p>Hi i am trying to delete a key value from the context for <code>res.partner</code> form view.</p>
  
  <p>I opening the <code>partner form view</code> using <code>controller</code> function and trying to set phone number as default and its working fine. But when i try to create a new customer by clicking on the create button the <code>phone</code> number again auto-filled. In order to avoid this behaviour, in <code>default_get</code> function, i copied the context into another variable,  removed the <code>key value</code> from the context using <code>del context['cc_mobile']</code>. And reassigned to <code>self.env.context</code>. But when i try to create a new customer, the deleted <code>key value</code> comes in the context again. </p>
  
  <p><strong>Controller.py</strong></p>
  
  <pre><code>@http.route('/open_customer/&lt;string:val&gt;', type="http",method=['POST','GET'],website=False, auth="public")
  def open_case_window(self,**kw):
      mobile_no = kw.get('val')
      action = request.env.ref('base.action_partner_form').sudo()
      mobile_flag = 0
      partner = 'res.partner'
      partner_model = request.env[partner]
      regex = re.match( '^(?:\01|02|03|04|06|07|09)\d*$', mobile_no)
      if regex:
          mobile_flag = 0
          partner_id = partner_model.search([('phone', '=', mobile_no)]).id
      else:
          mobile_flag = 1
          partner_id = partner_model.search([('mobile','=',mobile_no)]).id
  
      if partner_id:
          return werkzeug.utils.redirect('/web#id='+str(partner_id)+'&amp;view_type=form&amp;model='+partner)
      else:
          context = dict(action._context)
          if mobile_flag == 0:
              context.update({'cc_phone': mobile_no})
          else:
              context.update({'cc_mobile': mobile_no})
          context.pop('lang')
          url = werkzeug.utils.redirect('/web?debug=#view_type=form&amp;model='+str(partner)+'&amp;action=%s'%(action.id))
          return url
  </code></pre>
  
  <p><strong>ResPartner.py</strong></p>
  
  <pre><code> @api.model
  def default_get(self, fields):
      context = self.env.context.copy()
      print'default_get context',context
      res = super(Partner, self).default_get(fields)
      if 'cc_mobile' in context:
          res.update({'mobile':context.get('cc_mobile')})
      if 'cc_phone' in context:
          res.update({'phone':context.get('cc_phone')})
      if context.get('cc_mobile'):
          del context['cc_mobile']
      if context.get('cc_phone'):
          del context['cc_phone']
      self.env.context = context
      print'self.env.context after',self.env.context
      action = self.env.ref('base.action_partner_form').sudo()
      action.env.context = self.env.context
      return res
  </code></pre>