attachment_ids = fields.Many2many('ir.attachment', string='Files')
file = fields.Binary('file',string='file')
@api.multi
def get_path_file(self):
    path =""
    path = pathof(self.file)# here i want to get the path
    shutil.copy2(path+name_of_file, '/desktop/folder_copy')

in onchange or any method when i make a breakpoint i want to get path like this
( /home/Desktop/backup/files/myfile.pdf) from any system (linux ,windows ,MacOs)
NB : Odoo 12