TG_TABLE_NAME with NEW in a trigger function - postgresql

Question

I have a shared trigger function used by multiple tables.
Each tables's primary key uses the format pk_ + tablename i.e. pk_account or pk_order
How can I dynamically reference the NEW object column in a trigger using a variable?
CREATE OR REPLACE FUNCTION shared_test_trigger_fn()
RETURNS trigger AS
$$
DECLARE
primary_key TEXT DEFAULT CONCAT('pk_', TG_TABLE_NAME);
primary_value TEXT DEFAULT CONCAT('NEW.pk_', TG_TABLE_NAME);
BEGIN
RAISE NOTICE 'The PK field is called %', primary_key;
RAISE NOTICE 'The PK value is %', primary_value;
RETURN NEW;
END;
$$
LANGUAGE 'plpgsql';
DROP TRIGGER IF EXISTS account_test_trigger ON account;
CREATE TRIGGER account_test_trigger BEFORE UPDATE
ON account
FOR EACH ROW
EXECUTE PROCEDURE shared_test_trigger_fn();
UPDATE account SET created = created WHERE pk_account = 1;
EDIT1:
This trigger is simply an example to demonstrate the issue. The scenario is, we have a number of tables sharing a similar format with the PK field including the table name. Rather than code & maintain multiple similar trigger functions we are looking to have a single trigger function that can work with multiple tables.

Answer 1

It can be done fairly easy in plpython3u:
CREATE OR REPLACE FUNCTION public.pk_tablename()
RETURNS trigger
LANGUAGE plpython3u
AS $function$
pk = "pk_" + TD["table_name"]
pk_val = TD["new"][pk]
plpy.notice("PK value is " + str(pk_val))
$function$
CREATE TRIGGER trg_pk_tablename BEFORE UPDATE
ON animals
FOR EACH ROW
EXECUTE PROCEDURE pk_tablename();
animals
Table "public.animals"
Column | Type | Collation | Nullable | Default
------------+------------------------+-----------+----------+---------
pk_animals | integer | | not null |
cond | character varying(200) | | not null |
animal | character varying(200) | | not null |
Indexes:
"animals_pkey" PRIMARY KEY, btree (pk_animals)
Triggers:
trg_pk_tablename BEFORE UPDATE ON animals FOR EACH ROW EXECUTE FUNCTION pk_tablename()
update animals set cond = 'good' where pk_animals = 200;
NOTICE: PK value is 200
UPDATE 1
I have made attempts using plpgsql but have not found the magic sauce yet.