After installing a new instance of Odoo, in most of the cases would be needed to generate a new configuration file. That can be done with the following command line:

python odoo/odoo-bin -c <path-to-config> -d <database-name> -s --stop-after-init 

Once the configuration file is generated with the default values it can be customized according to the needs of the server. The customized configuration file can be used by specifying it during server startup in the following way:

python odoo/odoo-bin -c <path-to-config> -d <database-name>

In case the CSS​ is not loaded in the QWeb Reports, few System Parameters​ that may solve the issue are following:

• The system parameter web.base.url​ ​need to have as value the system's domain, in our case that is  https://odoomastery.com​
• The parameter web.base.url.freeze​ need to have as value True​
• The parameter report.url​ need to have as value the system's local host url, in many cases that would be http://localhost:8069​

The System Parameters​ menu can be found at:
Settings >> Technical >> Parameters >> System Parameters​.

In case we need to upgrade all installed modules in an Odoo instance, that can be done directly from the command line using the following command for Linux systems:

python odoo/odoo-bin -c <path-to-config> -d <database-name> -u all --stop-after-init

Should be mentioned that need to be used python​ from the environment that the Odoo instance is using. Also the Odoo server need to be stop before the upgrade is started.

Very good case when such upgrade is needed is when the Odoo source code is updated to more recent commit of the installed version.

The method has_group​ in the model res.users​ is helpful for checking if a user belongs to a specific group.

For example, if we need to check if a user is a salesman in the system, the code should look like this: 

# In this example we will use the current active user
# but can be browsed and used any available user in the system
# Ex: self.env['res.users'].browse(<user_id>)
user = self.env.user

if user.has_group('sales_team.group_sale_salesman'):
    print('This user is a salesman')

Another method that is useful when need to check the current user's group membership is user_has_groups​. This method is available in all models and it returns True​ if the user has at least one of the provided groups in groups​ not preceded by !​ and  is not a member of any of the groups in groups preceded by !​. 

An example of this method that will confirm that the current active user is a salesman but not a purchase manager is the following:

if self.user_has_groups('sales_team.group_sale_salesman,!purchase.group_purchase_manager'):
	​print('This user salesman but not purchase manager.')

There are cases when is needed to have a model that will not be represented by a table in the database. By default, Odoo creates a table for every Model​ and ​TransientModel​,  but, there is option to change that by setting up the attribute ​_auto​ to False​  

For example, If we want to create a new model PartnerContact​ that will have the base fields and methods for our PartnerCompany​ and ​PartnerPerson​ models the base definition of the model should look like: 

from odoo import models
 
class PartnerContact(models.Model):
    _name = 'partner.contact'
    _description = 'Partner Contact'
    _auto = False        

Another way of doing this is by inheriting the class AbstractModel​ which by default has the attribute ​_auto​ set to ​False​​

from odoo import models

class PartnerContact(models.AbstractModel):
    _name = 'partner.contact'
    _description = 'Partner Contact'

In case the total of a numeric column needs to be shown at the bottom of a list view, would be needed to include the attribute sum​ in the field’s XML definition.

For example, if amount​ field needs to have a total at the bottom of the column the XML code for this field in the list view would look like the following:

<field name="amount" sum="Total Amount"/>        

The string that is assigned to the sum​ attribute is the text that is shown on hover of the value.