wordfreq/scripts/gen_regex.py
Andrew Lin 05e14592af Tweaks to the regex generator for brevity:
* Don't repeat the logic that generates the ranges
  * Include only unassigned characters between two accepted ranges; this causes the resulting
    regexes to be a bit more readable.
  * Rearrange the script itself to avoid long lambdas and group helper functions together
  * Precompute the list of all the character classes for speed and terseness


Former-commit-id: cc6920d7e4
2015-07-08 15:29:31 -04:00

78 lines
2.5 KiB
Python

import unicodedata
from ftfy import chardata
import pathlib
from pkg_resources import resource_filename
CATEGORIES = [unicodedata.category(chr(i)) for i in range(0x110000)]
DATA_PATH = pathlib.Path(resource_filename('wordfreq', 'data'))
def func_to_regex(func):
"""
Given a function that returns True or False for a numerical codepoint,
return a regex character class accepting the characters resulting in True.
Ranges separated only by unassigned characters are merged for efficiency.
"""
# A list of [start, end (accepted), end (accepted or unassigned)] lists
ranges = []
for i, cat in enumerate(CATEGORIES):
if func(i):
# If the last range can be extended, do so; else start a new one
if ranges and ranges[-1][2] == i - 1:
ranges[-1][1] = i
ranges[-1][2] = i
else:
ranges.append([i, i, i])
elif cat == 'Cn':
# If the last range can be extended, do so
if ranges and ranges[-1][2] == i - 1:
ranges[-1][2] = i
return '[%s]' % ''.join(chr(r[0]) + '-' + chr(r[1]) for r in ranges)
def cache_regex_from_func(filename, func):
"""
Generates a regex from a function that accepts a single unicode character,
and caches it in the data path at filename.
"""
with (DATA_PATH / filename).open(mode='w') as f:
f.write(func_to_regex(func))
def _is_emoji_codepoint(i):
"""
Report whether a numerical codepoint is (likely) an emoji: a Unicode 'So'
character (as future-proofed by the ftfy chardata module) but excluding
symbols like © and ™ below U+2600 and the replacement character U+FFFD.
"""
return chardata.CHAR_CLASS_STRING[i] == '3' and i >= 0x2600 and i != 0xfffd
def _is_non_punct_codepoint(i):
"""
Report whether a numerical codepoint is not one of the following classes:
- P: punctuation
- S: symbols
- Z: separators
- C: control characters
This will classify symbols, including emoji, as punctuation; users that
want to accept emoji should add them separately.
"""
return CATEGORIES[i][0] not in 'PSZC'
def _is_combining_mark_codepoint(i):
"""
Report whether a numerical codepoint is a combining mark (Unicode 'M').
"""
return CATEGORIES[i][0] == 'M'
if __name__ == '__main__':
cache_regex_from_func('emoji.txt', _is_emoji_codepoint)
cache_regex_from_func('non_punct.txt', _is_non_punct_codepoint)
cache_regex_from_func('combining_mark.txt', _is_combining_mark_codepoint)