OVOS Number Parser
Convert numbers between digits and spoken words, in 40 languages, with one small dependency-light library.
"twenty twenty three" ⇄ 2023 ⇄ "two thousand, twenty three"
ovos-number-parser goes both ways:
- words to digits: turn spoken-form text into numbers
(
extract_number,numbers_to_digits). Use it for ASR post-processing / inverse text normalization and numeric entity extraction. - digits to words: turn numbers into natural spoken text
(
pronounce_number,pronounce_ordinal,pronounce_fraction). Use it for TTS normalization before synthesis.
It ships as part of the OpenVoiceOS voice stack. It
is plain Python with no assistant dependencies. Every example below runs
after a single pip install, with no voice assistant involved.
Install
pip install ovos-number-parser
# or, with uv:
uv pip install ovos-number-parser
30-second quickstart
from ovos_number_parser import (pronounce_number, pronounce_ordinal,
extract_number, numbers_to_digits,
is_fractional, is_ordinal)
# digits -> words
pronounce_number(3.5, "en") # 'three point five'
pronounce_number(2023, "en") # 'two thousand, twenty three'
pronounce_ordinal(21, "en") # 'twenty-first'
# words -> digits
extract_number("three point five liters", "en") # 3.5
extract_number("dos mil veintitrés", "es") # 2023
numbers_to_digits("set a timer for five minutes", "en") # 'set a timer for 5 minutes'
# classification helpers
is_fractional("half", "en") # 0.5
is_ordinal("third", "en") # 3
# no number in the text -> False
extract_number("hello world", "en") # False
Pass a different language code and the same calls work. See the matrix for the 40 supported languages.
What it's good for (beyond voice assistants)
The library is a standalone text/number utility. Four common uses, each with a
runnable script in examples/:
1. ASR post-processing / inverse text normalization
Speech-to-text emits numbers as words. Most downstream systems want digits.
from ovos_number_parser import numbers_to_digits, extract_number
numbers_to_digits("i need twenty three of them", "en") # 'i need 23 of them'
extract_number("three point five liters", "en") # 3.5
2. TTS normalization
Expand numbers into words before synthesis so the voice reads them naturally ("one thousand..." instead of "one-two-three-four dot five six").
from ovos_number_parser import pronounce_number
pronounce_number(1234.56, "en", places=2)
# 'one thousand, two hundred and thirty four point five six'
pronounce_number(-3.5, "en") # 'minus three point five'
→ examples/tts_normalization.py
3. Numeric entity extraction (NER)
Pull cardinal, ordinal and fractional mentions out of free text without an ML model.
from ovos_number_parser import extract_number, is_fractional, is_ordinal
extract_number("shipped in three boxes", "en") # 3
is_ordinal("second", "en") # 2
is_fractional("quarter", "en") # 0.25
4. Multilingual round-trips
The same two functions cover 40 languages, with dialect prefixes
(pt-BR, pt-PT → pt).
In an OVOS skill vs. standalone
The API is the same in both cases. Only where you get the language code differs.
# Standalone Python: you pass the language yourself
from ovos_number_parser import extract_number
n = extract_number(text, "en")
# Inside an OVOS skill: the framework already knows the session language
class MySkill(OVOSSkill):
def handle_intent(self, message):
n = extract_number(message.data["utterance"], self.lang)
Supported languages
40 languages. Every language supports every public function: where a
language has no hand-written implementation for a given function, a documented
generic fallback fills in (unicode-rbnf for pronunciation, reverse-lookup for
the rest: see Full function parity),
so the call always returns a sensible result rather than raising.
- Y: dedicated hand-written implementation
- ·: supported via the documented generic fallback
| Code | Language | pronounce_number | pronounce_ordinal | extract_number | numbers_to_digits | is_fractional | is_ordinal |
|---|---|---|---|---|---|---|---|
ar |
Arabic | Y | Y | Y | · | Y | Y |
an |
Aragonese | Y | Y | Y | Y | Y | Y |
ast |
Asturian | Y | Y | Y | Y | Y | Y |
az |
Azerbaijani | Y | · | Y | Y | Y | · |
eu |
Basque | Y | Y | Y | · | Y | Y |
bg |
Bulgarian | Y | · | Y | Y | Y | · |
ca |
Catalan | Y | · | Y | Y | Y | · |
hr |
Croatian | Y | Y | Y | Y | Y | · |
cs |
Czech | Y | Y | Y | Y | Y | · |
da |
Danish | Y | Y | Y | Y | Y | Y |
nl |
Dutch | Y | Y | Y | Y | Y | · |
en |
English | Y | · | Y | Y | Y | Y |
et |
Estonian | Y | Y | Y | · | Y | Y |
fi |
Finnish | Y | Y | Y | · | Y | Y |
fr |
French | Y | · | Y | · | Y | · |
gl |
Galician | Y | Y | Y | Y | Y | Y |
de |
German | Y | Y | Y | Y | Y | Y |
el |
Greek | Y | Y | Y | · | Y | Y |
he |
Hebrew | Y | Y | Y | · | Y | Y |
hu |
Hungarian | Y | Y | Y | · | Y | Y |
id |
Indonesian | Y | Y | Y | Y | Y | · |
it |
Italian | Y | · | Y | · | Y | · |
kab |
Kabyle | Y | Y | Y | · | Y | Y |
ms |
Malay | Y | Y | Y | Y | Y | · |
mwl |
Mirandese | Y | Y | Y | Y | Y | Y |
nb |
Norwegian Bokmål | Y | Y | Y | Y | Y | Y |
nn |
Norwegian Nynorsk | Y | Y | Y | Y | Y | Y |
oc |
Occitan | Y | Y | Y | Y | Y | Y |
fa |
Persian | Y | Y | Y | · | Y | · |
pl |
Polish | Y | Y | Y | Y | Y | · |
pt |
Portuguese | Y | Y | Y | Y | Y | Y |
ro |
Romanian | Y | Y | Y | Y | Y | Y |
ru |
Russian | Y | · | Y | Y | Y | · |
sk |
Slovak | Y | Y | Y | Y | Y | · |
sl |
Slovenian | Y | · | Y | · | Y | Y |
es |
Spanish | Y | · | Y | Y | Y | · |
sv |
Swedish | Y | Y | Y | · | Y | · |
tr |
Turkish | Y | Y | Y | Y | Y | · |
uk |
Ukrainian | Y | Y | Y | Y | Y | · |
fy |
West Frisian | Y | Y | Y | Y | Y | · |
Language-specific behaviour (compound-word splitting, vigesimal counting, grammatical gender, declensions, script handling) is documented in docs/languages.md.
Grammatical gender
Languages whose numerals inflect accept a gender argument:
from ovos_number_parser import pronounce_number
from ovos_number_parser.util import GrammaticalGender
pronounce_number(2, "pt", gender=GrammaticalGender.FEMININE) # 'duas'
Documentation
- API reference: every public function and its parameters
- Language notes: per-language behaviour and known gaps
- Adding a language: implementation guide
- examples/: runnable scripts (each ends with its verified output)
Related projects
- ovos-date-parser: dates and times
- ovos-lang-parser: languages
- ovos-color-parser: colors
License
Apache License 2.0.
1 maintainer
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