Spanish pronunciation rules in Pynini

spa_g2p.py

from typing import Optional

from pynini import *


def _rule(tau: Fst, sigma: Fst) -> Fst:
    return cdrewrite(tau, "", "", sigma).optimize()


def _right_rule(tau: Fst, right: Fst, sigma: Fst) -> Fst:
    return cdrewrite(tau, "", right, sigma).optimize()


# Alphabet.

front_v = union("i", "e")
back_v = union("a", "o", "u")
ph_v = front_v | back_v
gr_v = union("á", "é", "í", "ó", "ú", "ý")
ph_c = union("b", "tʃ", "d", "f", "g", "j", "k", "l", "ʝ", "m",
             "n", "ɲ", "p", "r", "ɾ", "R", "s", "t", "w", "x", "z")
gr_c = union("c", "h", "ñ", "q", "v", "y")
# Closure over the alphabet---neeeded to compile rewrite rules.
sigma = closure(ph_v | gr_v | ph_c | gr_c).optimize()


## START OF PART 4.

u_rules = _rule(string_map([
        # Digraphs.
        ("ch", "tʃ"),
        ("ll", "ʝ"),
        ("qu", "k"),
        # Removes acute accents.
        ("á", "a"),
        ("é", "e"),
        ("í", "i"),
        ("ó", "o"),
        ("ú", "u"),
        # Other unconditioned rules.
        ("v", "b"),
        ("ñ", "ɲ"),
    ]
), sigma)

# TODO(kbg): This is not quite right.
r_rules = ( 
    _rule(transducer("rr", "R"), sigma) @
    _rule(transducer("r", "ɾ"), sigma) @
    _rule(transducer("R", "r"), sigma)
).optimize()

b_rules = (
    _rule(transducer("x", "ks"), sigma) @
    _rule(transducer("j", "x"), sigma) @
    _rule(transducer(union("ý", "y"), "j"), sigma) @
    _rule(transducer("hi", "j"), sigma) @
    _rule(transducer("hu", "w"), sigma) @
    _rule(transducer("h", ""), sigma)
).optimize()

k_rules = (
    _right_rule(transducer("g", "x"), front_v, sigma) @
    _right_rule(transducer("gu", "g"), front_v, sigma) @
    _rule(transducer("gü", "gw"), sigma) @
    _right_rule(transducer("c", "s"), front_v, sigma) @
    _right_rule(transducer("cu", "kw"), ph_v, sigma) @
    _rule(transducer("c", "k"), sigma)
)

g2p = optimize(u_rules @ r_rules @ b_rules @ k_rules)


def _rewrite(s: str, rule: Fst) -> Optional[str]:
    lattice = compose(s, rule)
    if lattice.start() == NO_STATE_ID:
        return
    return shortestpath(lattice).stringify()


assert _rewrite("cuando", g2p) == "kwando"
assert _rewrite("hierba", g2p) == "jeɾba"
assert _rewrite("hacer", g2p) == "aseɾ"
assert _rewrite("llave", g2p) == "ʝabe"
assert _rewrite("pero", g2p) == "peɾo"