readsight 1.0.3

Multilingual readability library for Python — 86 languages, 17 formulas, TeX-based syllable counting via Frank M. Liang algorithm.

ReadSightPy — Multilingual Readability Engine for Python

ReadSightPy measures text readability across 86 languages using 17 readability formulas with language-specific coefficients. Syllable counting is powered by the Frank M. Liang (TeX) hyphenation algorithm — the same algorithm used by TeX for decades. All with zero heavy dependencies.

This is a Python port of ReadSight (PHP).

Table of Contents

• Installation
• Quick Start
• Demo
• Supported Languages
• Readability Formulas
• FormulaResult
• Performance
• Custom Configuration
• Architecture
• Data Sources
• Development
• License

Installation

pip install readsight

Requirements:

• Python >= 3.10
• regex (for Unicode regex \p{L} support)
• platformdirs (for cache directory)

No other runtime dependencies.

Quick Start

from readsight import ReadSight

rs = ReadSight("en-us")

# Syllable counting
rs.syllable_count("banana")         # 3
rs.split_syllables("hyphenation")   # ['hyp', 'hen', 'ati', 'on']  (4 syllables, heuristic split)
rs.split_word("hyphenation")        # ['hy', 'phen', 'a', 'tion']  (TeX hyphenation points)

# Text analysis
stats = rs.analyze("The quick brown fox jumps over the lazy dog.")
print(f"Words: {stats.word_count}, Syllables: {stats.syllable_count}")

# Readability formulas
fre = rs.flesch_reading_ease(text)
print(f"Flesch Reading Ease: {fre.score} - {fre.interpretation}")

fog = rs.gunning_fog(text)
print(f"Gunning Fog: {fre.score} (grade {fre.grade_level})")

lix = rs.lix(text)
print(f"LIX: {fre.score} - {fre.interpretation}")

Syllable Counting Modes

ReadSightPy has three syllable counting modes, configured per language via syllableMode in data/languages/*.json:

Mode	How it works	count accuracy	split accuracy
heuristic	Vowel patterns + word list + prefix/suffix rules	✓	≈ approximate
tex	Frank M. Liang hyphenation algorithm (TeX .tex patterns)	✓	✓ exact
composite	Heuristic first, TeX as fallback	✓	≈ approximate (uses heuristic split)

80 languages use tex, 4 use composite (en-us, en-gb, it, pl), 2 use heuristic.

Example: "hyphenation" in each mode

rs = ReadSight("en-us")   # composite mode — heuristic wins
rs.syllable_count("hyphenation")   # 4 ✓ (in problemWords list)
rs.split_syllables("hyphenation")  # ['hyp', 'hen', 'ati', 'on']   — heuristic: equal-width split, ≈ approximate
rs.split_word("hyphenation")       # ['hy', 'phen', 'a', 'tion']   — TeX hyphenator: exact points

rs = ReadSight("de-1996")  # tex mode
rs.syllable_count("hyphenation")   # 4 ✓ (TeX patterns)
rs.split_syllables("hyphenation")  # ['hy', 'phen', 'a', 'tion']   — TeX: exact
rs.split_word("hyphenation")       # ['hy', 'phen', 'a', 'tion']   — same, both use TeX

Tip: split_word() always uses the TeX hyphenator (exact). split_syllables() may use heuristic (approximate). For syllable counts both are correct.

Note: add_hyphenations() adds overrides to the TeX hyphenator. These affect split_word() but NOT split_syllables() in composite/heuristic modes (the heuristic counter doesn't see them).

Demo

Run the interactive demo to see ReadSightPy in action:

python examples/demo.py

This analyzes built-in sample text and outputs:

• Syllable breakdown with hyphenation points for common words
• Text statistics — letters, words, sentences, syllables, histogram
• All applicable readability formulas with scores and interpretations

Compare the same text across 6 languages:

# Built into demo.py — runs multilingual comparison automatically
python examples/demo.py

Supported Languages

86 languages across 19 writing systems: Latin, Cyrillic, Arabic, Hebrew, Devanagari, Bengali, Tamil, Thai, Greek, Armenian, Georgian, Gujarati, Gurmukhi, Kannada, Malayalam, Odia, Telugu, Ethiopic, Coptic.

rs = ReadSight("ru")        # Russian
rs = ReadSight("de-1996")   # German (1996 reform)
rs = ReadSight("es")        # Spanish
rs = ReadSight("th")        # Thai

# List all supported languages
langs = ReadSight.get_supported_languages()
# ['af', 'ar', 'as', 'be', 'bg', 'bn', 'ca', 'cop', 'cs', 'cu', 'cy', 'da',
#  'de-1901', 'de-1996', 'de-ch-1901', 'el-monoton', 'el-polyton', 'en-gb',
#  'en-us', 'eo', 'es', 'et', 'eu', 'fa', 'fi', 'fi-x-school', 'fr', 'fur',
#  'ga', 'gl', 'grc', 'gu', 'he', 'hi', 'hr', 'hsb', 'hu', 'hy', 'ia', 'id',
#  'is', 'it', 'ka', 'kk', 'kmr', 'kn', 'la', 'la-x-classic', 'la-x-liturgic',
#  'lt', 'lv', 'mk', 'ml', 'mn-cyrl', 'mn-cyrl-x-lmc', 'mr', 'mul-ethi', 'nb',
#  'nl', 'nn', 'oc', 'or', 'pa', 'pi', 'pl', 'pms', 'pt', 'rm', 'ro', 'ru',
#  'sa', 'sh-cyrl', 'sh-latn', 'sk', 'sl', 'sq', 'sr-cyrl', 'sv', 'ta', 'te',
#  'th', 'tk', 'tr', 'uk', 'vi', 'zh-latn-pinyin']

Readability Formulas

Universal (all 86 languages)

Formula	Method	Type	Score Range
Gunning Fog	gunning_fog()	Syllable-based	0–20+
SMOG Index	smog_index()	Syllable-based	3–18+
Coleman-Liau	coleman_liau()	Letter-based	0–18+
ARI	automated_readability_index()	Letter-based	0–18+
LIX	lix()	Letter-based	20–60+

Language-Specific

Language	Formulas
English (en-us, en-gb)	Flesch Reading Ease, FK Grade Level, Dale-Chall*, Spache*
German (de-*)	Flesch Reading Ease (Amstad), FKGL, Wiener Sachtextformel (4 variants)
Russian (ru)	Flesch Reading Ease (Oborneva), FKGL
Spanish (es)	Flesch Reading Ease, Fernandez-Huerta, Szigriszt-Pazos, Gutierrez-Polini, Crawford
Italian (it)	Flesch Reading Ease, Gulpease
French (fr)	Flesch Reading Ease (Kandel-Moles)
Dutch (nl)	Flesch Reading Ease (Douma)
Portuguese (pt)	Flesch Reading Ease (Martins)
Turkish (tr)	Flesch Reading Ease (Ateşman)
Polish (pl)	FOG-PL
Arabic (ar)	OSMAN

*Note: Dale-Chall and Spache formulas use a syllable-based heuristic to estimate difficult words (1-syllable ≈ easy). This is a simplified estimation, not based on the original Dale/Spache word lists.

Generic dispatching:

result = rs.score("gunning_fog", text)
result = rs.score("wiener_sachtextformel", text)

FormulaResult

result.score           # float — raw formula score
result.grade_level     # float | None — normalized grade level (FKGL, GF, SMOG, CL, ARI)
result.interpretation  # str — qualitative interpretation ("Easy", "Hard")
result.formula_name    # str — formula key
result.language_code   # str — language code used
result.inputs          # dict[str, float | int] — intermediate values for debugging

API Reference

Text Analysis Methods

rs.syllable_count(word: str) -> int
rs.split_syllables(word: str) -> list[str]
rs.split_word(word: str) -> list[str]
rs.word_count(text: str) -> int
rs.sentence_count(text: str) -> int
rs.letter_count(text: str) -> int
rs.total_syllables(text: str) -> int
rs.average_syllables_per_word(text: str) -> float
rs.average_words_per_sentence(text: str) -> float
rs.polysyllable_count(text: str, count_proper_nouns: bool = True) -> int
rs.words_with_more_than_n_syllables(text: str, n: int, count_proper_nouns: bool = True) -> int
rs.histogram_syllables(text: str) -> dict[int, int]
rs.analyze(text: str) -> TextStatistics

split_syllables vs split_word: split_syllables may use heuristic ≈approximate split (depends on language's syllableMode). split_word always uses the TeX hyphenator for exact hyphenation points. Syllable counts are accurate in all modes. See Syllable Counting Modes.

Formula Methods

rs.flesch_reading_ease(text: str) -> FormulaResult
rs.flesch_kincaid_grade_level(text: str) -> FormulaResult
rs.gunning_fog(text: str) -> FormulaResult
rs.smog_index(text: str) -> FormulaResult
rs.coleman_liau(text: str) -> FormulaResult
rs.automated_readability_index(text: str) -> FormulaResult
rs.lix(text: str) -> FormulaResult
rs.wiener_sachtextformel(text: str, variant: int = 1) -> FormulaResult
rs.gulpease(text: str) -> FormulaResult
rs.fernandez_huerta(text: str) -> FormulaResult
rs.szigriszt_pazos(text: str) -> FormulaResult
rs.gutierrez_polini(text: str) -> FormulaResult
rs.crawford(text: str) -> FormulaResult
rs.fog_pl(text: str) -> FormulaResult
rs.dale_chall(text: str) -> FormulaResult
rs.spache(text: str) -> FormulaResult
rs.osman(text: str) -> FormulaResult

Performance

Measured on CPython 3.12, Intel Core i7 (limited data — full benchmarks TBD):

Operation	Time
Syllable counting (single word)	~0.05 ms
Text analysis (45 words)	~1 ms
Formula calculation (incl. analysis)	~1 ms
Engine init (en-us, cached)	~10 ms
Engine init (de-1996, first load)	~60 ms

Caching: compiled patterns are stored as JSON in the system cache directory (platformdirs.user_cache_dir). First load parses .tex files (native hyph-utf8 format); subsequent loads use the pre-compiled cache.

Custom Configuration

from readsight import ReadSight, Config

# Set default paths (before creating engines)
ReadSight.set_default_config(Config(
    patterns_dir="/custom/patterns",
    languages_dir="/custom/languages",
    cache_dir="/var/cache/readsight",
))

# Or per-instance
rs = ReadSight(
    language="en-us",
    patterns_dir="/custom/patterns",
    cache_dir="/custom/cache",
)

# Add custom hyphenation rules (affects split_word, not split_syllables)
rs.add_hyphenations({
    "customword": "cus-tom-word",
})
rs.split_word("customword")  # ['cus', 'tom', 'word']

Architecture

ReadSight (facade)
  ├── TextAnalyzer (syllable counting, text metrics)
  │   ├── SyllableCounter (strategy: tex | heuristic | composite)
  │   │   ├── CompositeSyllableCounter (problemWords → heuristic, rest → TeX)
  │   │   ├── HeuristicSyllableCounter (vowel patterns + word list)
  │   │   └── TexSyllableCounter → LiangHyphenator (TeX hyphenation)
  │   ├── LiangHyphenator
  │   │   ├── TexSource (parses .tex from hyph-utf8)
  │   │   ├── PatternsCollection (pattern data)
  │   │   ├── HyphenationExceptionsCollection (word overrides)
  │   │   └── JsonPatternCache (compiled patterns)
  │   └── TextSplitter (word/sentence/letter counting)
  ├── Language (JSON config per language, syllableMode + formulaConfigs)
  └── FormulaRegistry (17 formulas)
      ├── FleschReadingEase (with lang-specific coefficients)
      ├── GunningFog, SMOG, ColemanLiau, ARI, LIX (universal)
      └── WSTF, Gulpease, Fernandez-Huerta, etc. (lang-specific)

Data Sources

• TeX hyphenation patterns: hyph-utf8 version 2026-02-21 — the canonical TeX hyphenation repository maintained by the TeX Users Group (TUG). 86 .tex pattern files from hyph-utf8 covering 86 language variants. Packaged under each pattern file's original license.
• FRE coefficients: Amstad (DE), Oborneva (RU), Fernandez-Huerta (ES), Vacca-Franchina (IT), Kandel-Moles (FR), Douma (NL), Martins (PT), Ateşman (TR)
• WSTF: Bamberger & Vanecek (DE)
• Gulpease: GULP, La Sapienza University (IT)

Development

pip install -e ".[dev]"    # Install with dev dependencies

pytest                     # Run all tests (133 tests)
pytest --cov=readsight     # With coverage report
mypy src/                  # Static type checking (strict mode)
ruff check src/ tests/     # Lint
ruff format src/ tests/    # Format

Quality Metrics

Metric	Value
Tests	133
Mypy	Strict mode, 0 errors
Ruff	0 errors
Source files	56
Test files	18
Supported languages	86
Writing systems	19
Readability formulas	17
Runtime dependencies	2 (regex, platformdirs)

License

MIT. Author: Yevhen Leonidov.

TeX pattern files from hyph-utf8 are packaged under their original licenses (see individual file headers).