Go-Sentiment / scripts /tokenizer.py
SAKSHAM JOSHI
Create tokenizer.py
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from __future__ import annotations
import re
import unicodedata
from typing import Dict, List, Optional, Tuple
# --------------------------------------------------------------------------
# Script tables, generated from unicodedata so nothing is typed by hand
# --------------------------------------------------------------------------
# Code point blocks per script. Only the blocks are listed here; which
# characters inside them count as letters or digits comes from the category.
_SCRIPT_BLOCKS: Dict[str, List[Tuple[int, int]]] = {
"latin": [(0x0030, 0x0039), (0x0041, 0x005A), (0x0061, 0x007A),
(0x00C0, 0x024F), (0x0300, 0x036F), (0x1E00, 0x1EFF)],
"devanagari": [(0x0900, 0x097F)],
"bengali": [(0x0980, 0x09FF)],
"gurmukhi": [(0x0A00, 0x0A7F)],
"gujarati": [(0x0A80, 0x0AFF)],
"odia": [(0x0B00, 0x0B7F)],
"tamil": [(0x0B80, 0x0BFF)],
"telugu": [(0x0C00, 0x0C7F)],
"kannada": [(0x0C80, 0x0CFF)],
"malayalam": [(0x0D00, 0x0D7F)],
"arabic": [(0x0600, 0x06FF), (0x0750, 0x077F), (0x08A0, 0x08FF),
(0xFB50, 0xFDFF), (0xFE70, 0xFEFF)],
}
Ranges = List[Tuple[int, int]]
def _to_ranges(codepoints: List[int]) -> Ranges:
"""Collapse a list of code points into inclusive (lo, hi) ranges."""
out: Ranges = []
for cp in sorted(codepoints):
if out and cp == out[-1][1] + 1:
out[-1] = (out[-1][0], cp)
else:
out.append((cp, cp))
return out
def _build_tables() -> Dict[str, Tuple[Ranges, List[Ranges]]]:
"""script -> (letter ranges, [digit ranges, one entry per set of ten])."""
tables = {}
for script, blocks in _SCRIPT_BLOCKS.items():
letters: List[int] = []
digit_sets: Dict[int, List[int]] = {}
for lo, hi in blocks:
for cp in range(lo, hi + 1):
ch = chr(cp)
cat = unicodedata.category(ch)
if cat[0] in "LM":
letters.append(cp)
elif cat == "Nd":
# group by the "zero" of the set, so Arabic-Indic and
# Extended Arabic-Indic digits stay separate tokens
digit_sets.setdefault(cp - unicodedata.decimal(ch), []).append(cp)
tables[script] = (
_to_ranges(letters),
[_to_ranges(d) for _, d in sorted(digit_sets.items())],
)
return tables
_TABLES = _build_tables()
def export_tables() -> dict:
"""Plain-data copy of the script tables, for generating the TS/Java port."""
return {
"unicode_version": unicodedata.unidata_version,
"scripts": {
name: {
"letters": [list(r) for r in letters],
"digit_sets": [[list(r) for r in ds] for ds in digits],
}
for name, (letters, digits) in _TABLES.items()
},
}
def _esc(cp: int) -> str:
return f"\\u{cp:04x}" if cp <= 0xFFFF else f"\\U{cp:08x}"
def _class_body(ranges: Ranges) -> str:
return "".join(_esc(lo) if lo == hi else f"{_esc(lo)}-{_esc(hi)}" for lo, hi in ranges)
# --------------------------------------------------------------------------
# Characters allowed inside a word
# --------------------------------------------------------------------------
_JOINER = r"[\u200c\u200d]"
_APOSTROPHE = r"[\u0027\u2019\u02bc]"
# --------------------------------------------------------------------------
# Token pattern
# --------------------------------------------------------------------------
def _word(body: str) -> str:
# letters, optionally with ZWJ/ZWNJ between two letters
return rf"[{body}]+(?:{_JOINER}[{body}]+)*"
def _build_token_regex() -> "re.Pattern[str]":
"""Matches words and emojis only.
Numbers, punctuation and other symbols have no alternative here, so
findall() steps over them and they never reach the returned list.
"""
alts: List[str] = []
known: List[str] = []
# Latin first, it is the most common case
order = ["latin"] + [s for s in _TABLES if s != "latin"]
for script in order:
letters, _ = _TABLES[script]
body = _class_body(letters)
known.append(body)
if script == "latin":
alts.append(rf"[{body}]+(?:{_APOSTROPHE}[{body}]+)*")
else:
alts.append(_word(body))
keycap = r"[0-9#*]\ufe0f?\u20e3"
flag = r"[\U0001f1e6-\U0001f1ff]{2}"
emo_base = (r"[\u00a9\u00ae\u203c\u2049\u2122\u2139\u2194-\u21aa\u231a-\u23ff\u24c2"
r"\u25aa-\u25fe\u2600-\u27bf\u2934\u2935\u2b05-\u2b55\u3030\u303d"
r"\u3297\u3299\U0001f000-\U0001faff]")
skin = r"[\U0001f3fb-\U0001f3ff]"
emoji = (rf"{emo_base}\ufe0f?{skin}?"
rf"(?:\u200d{emo_base}\ufe0f?{skin}?)*"
r"[\U000e0020-\U000e007f]*")
# a few plain-text emoticons: :) :( :D :P ;) :-) :'( and <3
emoticon = (r"(?:[:;=][-']?(?:\)+|\(+|[DPp](?![A-Za-z0-9]))"
r"|(?<![A-Za-z0-9])<3+(?![0-9]))")
# best-effort for scripts we do not list (Cyrillic, Greek, CJK, ...):
# a run of letters that is not one of our known scripts
other = rf"(?:(?![{''.join(known)}])[^\W\d_])+"
parts = alts + [keycap, flag, emoji, emoticon, other]
return re.compile("|".join(parts))
_TOKEN = _build_token_regex()
# --------------------------------------------------------------------------
# URLs and e-mail addresses
# --------------------------------------------------------------------------
_LOCAL = r"A-Za-z0-9!#$%&'*+/=?^_`{|}~\-\u00c0-\u024f"
_LABEL = r"[A-Za-z0-9](?:[A-Za-z0-9-]{0,61}[A-Za-z0-9])?"
_EMAIL = (
r"(?:mailto:)?"
rf"(?<![{_LOCAL}.])"
rf"[{_LOCAL}]+(?:\.[{_LOCAL}]+)*"
rf"@(?:{_LABEL}\.)+[A-Za-z]{{2,}}"
)
# URL characters are ASCII only. If a Hindi word follows a URL with no space
# between them, the word is not swallowed. The price is that URLs containing
# raw non-ASCII characters are cut at the first one.
_CH = r"[^\s()<>\"'\u0080-\U0010ffff]"
_END = r"[^\s()<>\"'.,;:!?*\]}\u0080-\U0010ffff]"
_TAIL = rf"(?:{_CH}|\({_CH}*\))*(?:\({_CH}*\)|{_END})"
_URL = (
r"(?:(?i:https?|ftps?)://|(?<![A-Za-z0-9])(?i:www)\.)"
+ _TAIL
)
# bare domains only when a path follows (bit.ly/xyz), and only for common TLDs,
# so "Mr.Smith/John" is left alone
_TLDS = (r"(?i:com|net|org|edu|gov|info|biz|io|co|in|me|ly|gl|tv|ai|app|dev|xyz"
r"|us|uk|be|to|link|page|site|online|store)")
_BARE = (
r"(?<![A-Za-z0-9.@_\-])"
rf"(?:{_LABEL}\.)+{_TLDS}(?![A-Za-z0-9])"
rf"/(?:{_TAIL})?"
)
_PATTERN = re.compile(rf"{_EMAIL}|{_URL}|{_BARE}")
_GATE = re.compile(r"[@/]|www\.", re.IGNORECASE)
_SPACES = re.compile(r"[ \t]{2,}")
def _remove_urls_and_emails(
text: str,
replacement: str = " ",
collapse_spaces: bool = False,
) -> str:
"""Remove (or replace) URLs and e-mail addresses in `text`.
The replacement defaults to a space so the words on either side of a
removed URL never end up glued together.
"""
if not text:
return text
if _GATE.search(text):
text = _PATTERN.sub(replacement, text)
if collapse_spaces:
text = _SPACES.sub(" ", text).strip()
return text
# --------------------------------------------------------------------------
# Public API
# --------------------------------------------------------------------------
# curly apostrophe and modifier-letter apostrophe -> plain apostrophe
_APOS_FOLD = str.maketrans({0x2019: "'", 0x02BC: "'"})
def senti_vox_tokenizer(
text: str,
*,
normalize: Optional[str] = "NFKC",
lowercase: bool = True,
) -> List[str]:
"""Split `text` into word and emoji tokens.
Words are letter runs in any script (with ZWJ/ZWNJ inside Indic words and
apostrophes inside Latin ones). Emojis include ZWJ sequences, skin tones,
flags, keycaps and a few text emoticons like :) and <3. Numbers,
punctuation, other symbols, URLs and e-mail addresses are dropped.
normalize Unicode normal form applied first ("NFKC" by default, None to
skip). It also folds curly apostrophes to a plain one.
lowercase Lowercase the text before tokenizing. Off by default, in case
casing is handled on the lookup side.
Raises TypeError for anything that is not a str (None included).
"""
if not isinstance(text, str):
raise TypeError(f"senti_vox_tokenizer expects str, got {type(text).__name__}")
if not text:
return []
# pure ASCII text needs neither normalisation nor apostrophe folding
if normalize and not text.isascii():
text = unicodedata.normalize(normalize, text).translate(_APOS_FOLD)
text = _remove_urls_and_emails(text)
if lowercase:
text = text.lower()
return _TOKEN.findall(text)