My question is:
I am automatically tagging customers depending on the analytic account from sales orders. Does a .write() always write on the record even when the value is already there? Should I be doing a check with an if statement to see if the tag has already been set? If so, how do I check that? I tried a few things and couldn't figure it out.

*Edit: I should have noted that my code is working well but I'm just wondering if I should be checking if the category_id value is already there before the write happens and if so how to check. I am still very much in the  learning stage of Odoo development*

My code:

contact_tag_id = None
project_id = record.project_id.id
project_id_name = record.project_id.name
partner_id = record.partner_id.commercial_partner_id.id

if project_id == 44:
        contact_tag_id = 4
if project_id == 49:
        contact_tag_id = 6
if project_id == 48:
        contact_tag_id = 3
#Add the tag to contact
if contact_tag_id != None:
        project_id = contact_tag_id
        env['res.partner'].search([('id','=',partner_id)]).sudo().write({'category_id': [(4, contact_tag_id)]})