Sqlite join columns on mapping of values - python-3.x

Question

I want to be able to join two tables, where there is a mapping between the column values, rather than their values matching.
So rather than:
A|m | f B|m | f
a1 1 b1 1
a2 2 b2 3
a3 3 b3 5
SELECT a1, a2, b1, b2
FROM A
INNER JOIN B on B.f = A.f
giving:
|m| A.f B.f |m|
a1 1 1 b1
a3 3 3 b2
Given then mapping (1->a)(2->b)(3->c)
A|m | f B|m | f
a1 1 b1 a
a2 2 b2 b
a3 3 b3 c
to give when joined on f:
|m| A.f B.f |m|
a1 1 a b1
a3 3 c b2
The question below seems to be trying something similar, but they seem to want to change the column values, I just want the mappng to be part of the query, I don't want to change the column values thenselves. Besides it is in R and I'm working in Python.
Mapping column values

Answer 1

One solution is to create a temporary table of mappings AB:
CREATE TEMP TABLE AB (a TEXT, b TEXT, PRIMARY KEY(a, b));
Then insert mappings,
INSERT INTO temp.AB VALUES (1, "a"), (2, "b"), (3, "c");
or executemany with params.
Then select using intermediary table.
SELECT A.m AS Am, A.f AS Af, B.f AS Bf, B.m AS Bm
FROM A
LEFT JOIN temp.AB ON A.f=AB.a
LEFT JOIN B ON B.f=AB.b;
If you don't want to create an intermediary table, another solution would be building the query yourself.
mappings = ((1,'a'), (3,'c'))
sql = 'SELECT A.m AS Am, A.f AS Af, B.f AS Bf, B.m AS Bm FROM A, B WHERE ' \
+ ' OR '.join(['(A.f=? AND B.f=?)'] * len(mappings))
c.execute(sql, [i for m in mappings for i in m])