>>> import psycopg2
>>> conn = pyscopg2.connect("dbname=phil user=phil")
>>> cur = conn.cursor()
>>> cur.execute("CREATE TABLE some_table(id serial PRIMARY KEY, some_val text);")
>>> cur.execute("CREATE FUNCTION some_func(val text) RETURNS int AS $$ INSERT INTO some_table(some_val) SELECT $1 RETURNING id; $$LANGUAGE SQL;")
>>> cur.callproc("some_func", {"val": "fun times"})
>>> cur.fetchone()
(1,)
>>> cur.execute("CREATE FUNCTION some_other_func(text) RETURNS int AS $$ INSERT INTO some_table(some_val) SELECT $1 RETURNING id; $$LANGUAGE SQL;")
>>> cur.callproc("some_other_func", {"val": "fun times"})
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
psycopg2.ProgrammingError: function some_other_func(val => unknown) does not exist
LINE 1: SELECT * FROM some_other_func("val":='fun times')
                      ^
HINT:  No function matches the given name and argument types. You might need to add explicit type casts.