To create a Python code server action, follow these steps:

1. Create a new server action. In the Settings menu, select the Technical | Actions | Server Actions menu item, and click on the Create button at the top of the record list.
2. Fill out the Server Action form with the following values:
   • Action Name: Send Reminder
   • Base Model: Task
   • Action To Do: Execute Python Code

3. In the Python code text area, remove the default text and replace it with the following code:

if not record.date_deadline: 
    raise Warning('Task has no deadline!') 
delta = record.date_deadline - datetime.date.today() 
days = delta.days 
if days==0: 
    msg = 'Task is due today.' 
elif days < 0: 
    msg = 'Task is %d day(s) late.' % abs(days) 
else: 
    msg = 'Task will be due in %d day(s).' % days 
record.message_post(body=msg, subject='Reminder', subtype='mt_comment') 

The following screenshot shows the entered values:

4. Save the Server Action and click on Create Contextual Action in the top-right to make it available in the project task's More button.
5. Now, click on the Project top menu and select the Search|Tasks menu item. Pick a random task, set a deadline date on it, and then try the Send Reminder option in the More button.