• model is the name of the model, example: 'account.invoice'
• field is the name of the field inside the model, example: 'state'
• field_val is the value of that field, example: 'draft'

Code:

dict(self.pool.get(model).fields_get(cr, uid, allfields=[field], context=context)[field]['selection'])[field_val]

Example:

dict(self.pool.get('account.invoice').fields_get(cr, uid, allfields=['state'], context=context)['state']['selection'])['draft']

I use another technique.

First I define the list of pairs code/value

VALUES = [('a', 'A'), ('b','B'), ('c','C')]

I use it into my field definition

f = fields.Selection(VALUES)

and to return value, given the code, with a dict

dict(VALUES)[self.f]

or with a simple loop

for item in VALUES:
    if item[0] == self.f:
         return item[1]

The V8 way:

use the @api.one decorator

• current model :value = dict(self.fields_get(allfields=['state'])['state']['selection'])['key']

• other model : value = dict(self.env['your.model'].fields_get(allfields=['state'])['state']['selection'])['key']

Hope this help somebody..

you can use this.

dict(self._fields['your_selection_field'].selection).get(self.your_selection_field)

Checkout: https://www.odoo.com/forum/help-1/question/selection-field-label-42889

I use another technique.

First I define the list of pairs code/value

VALUES = [('a', 'A'), ('b','B'), ('c','C')]

I use it into my field definition

f = fields.Selection(VALUES)

and to return value, given the code, with a dict

dict(VALUES)[self.f]

or with a simple loop

for item in VALUES:
    if item[0] == self.f: