I also played with the same idea some time ago: https://github.com/akalenuk/fakelisp

I ended up using tuples instead of lists for cosmetic purposes :-) My Fakelisp then looks like this:

    from fakelisp import *
    
    # And now you can start mixing Python and LISP
    X = (BEGIN
        (SET (F) (LAMBDA (X)
            (IF (EQ (X) (1))
                (1)
                (MUL (X) (F (SUB (X) (1)))))))

        (LIST (F (4)) (42)))

    # Back to Python any time
    print "x: ", str(X)