User Errors and Warnings

When processing a request, you can stop the flow by raising an exception that will be displayed to the user as an error message or a warning. They are respectively UserError and UserWarning.

User Errors

An error displays a message and optionally a description to the user.

Example:

from trytond.exceptions import UserError
from trytond.model import Model

class MyModel(Model):
    "My Model"
    __name__ = 'my_model'

    def process(self):
        if check_failed:
            raise UserError("You cannot process.", "because…")

Note

They are often used in combination with gettext() to translate the messages.

User Warnings

A warning displays a confirmation message with optionally a description to the user. The user can decide to continue so the request is processed again without stopping at the warning. Otherwise the user can cancel its request. The warning instance is identified by a name which allows to skip it the next time it is checked, that’s why they often build using the format method which uses record instances to generate a unique name based on ids.

Example:

from trytond.exceptions import UserWarning
from trytond.model import Model
from trytond.pool import Pool

class MyModel(Model):
    "My Model"
    __name__ = 'my_model'

    def process(self):
        Warning = Pool().get('res.user.warning')
        warning_name = Warning.format('mywarning', [self])
        if Warning.check(warning_name):
            raise UserWarning(warning_name, "Process cannot be canceled.")

Note

If there is no user interaction the warnings can be skipped by setting the _skip_warnings key of the context to True.