fastai_transforms.py

'''
NLP data processing; tokenizes text and creates vocab indexes

I have directly COPIED AND PASTE OF THE TRANSFORMS.PY FASTAI LIBRARY.  I only
need the Tokenizer and the Vocab classes which are both in this module. This
way I avoid the numerous fastai dependencies.

Credit for the code here to Jeremy Howard and the fastai team
'''

from ..wdtypes import *

import sys
import os
import re
import html
import torch
import spacy

from concurrent.futures.process import ProcessPoolExecutor
from collections import Counter, defaultdict
from spacy.symbols import ORTH


def partition(a:Collection, sz:int)->List[Collection]:
    "Split iterables `a` in equal parts of size `sz`"
    return [a[i:i+sz] for i in range(0, len(a), sz)] # type: ignore


def partition_by_cores(a:Collection, n_cpus:int)->List[Collection]:
    "Split data in `a` equally among `n_cpus` cores"
    return partition(a, len(a)//n_cpus + 1)


def ifnone(a:Any,b:Any)->Any:
    "`a` if `a` is not None, otherwise `b`."
    return b if a is None else a


def num_cpus()->Optional[int]:
    "Get number of cpus"
    try:
        return len(os.sched_getaffinity(0))
    except AttributeError:
        return os.cpu_count()

_default_cpus = min(16, num_cpus())
defaults = SimpleNamespace(cpus=_default_cpus, cmap='viridis', return_fig=False, silent=False)

__all__ = ['BaseTokenizer', 'SpacyTokenizer', 'Tokenizer', 'Vocab', 'fix_html', 'replace_all_caps', 'replace_rep', 'replace_wrep',
           'rm_useless_spaces', 'spec_add_spaces', 'BOS', 'EOS', 'FLD', 'UNK', 'PAD', 'TK_MAJ', 'TK_UP', 'TK_REP', 'TK_REP', 'TK_WREP',
           'deal_caps']

BOS,EOS,FLD,UNK,PAD = 'xxbos','xxeos','xxfld','xxunk','xxpad'
TK_MAJ,TK_UP,TK_REP,TK_WREP = 'xxmaj','xxup','xxrep','xxwrep'
defaults.text_spec_tok = [UNK,PAD,BOS,EOS,FLD,TK_MAJ,TK_UP,TK_REP,TK_WREP]


class BaseTokenizer():
    "Basic class for a tokenizer function."
    def __init__(self, lang:str):                      self.lang = lang
    def tokenizer(self, t:str) -> List[str]:           return t.split(' ')
    def add_special_cases(self, toks:Collection[str]): pass


class SpacyTokenizer(BaseTokenizer):
    "Wrapper around a spacy tokenizer to make it a `BaseTokenizer`."
    def __init__(self, lang:str):
        self.tok = spacy.blank(lang, disable=["parser","tagger","ner"])

    def tokenizer(self, t:str) -> List[str]:
        return [t.text for t in self.tok.tokenizer(t)]

    def add_special_cases(self, toks:Collection[str]):
        for w in toks:
            self.tok.tokenizer.add_special_case(w, [{ORTH: w}])


def spec_add_spaces(t:str) -> str:
    "Add spaces around / and # in `t`. \n"
    return re.sub(r'([/#\n])', r' \1 ', t)


def rm_useless_spaces(t:str) -> str:
    "Remove multiple spaces in `t`."
    return re.sub(' {2,}', ' ', t)


def replace_rep(t:str) -> str:
    "Replace repetitions at the character level in `t`."
    def _replace_rep(m:Match[str]) -> str:
        c,cc = m.groups()
        return f' {TK_REP} {len(cc)+1} {c} '
    re_rep = re.compile(r'(\S)(\1{3,})')
    return re_rep.sub(_replace_rep, t)


def replace_wrep(t:str) -> str:
    "Replace word repetitions in `t`."
    def _replace_wrep(m:Match[str]) -> str:
        c,cc = m.groups()
        return f' {TK_WREP} {len(cc.split())+1} {c} '
    re_wrep = re.compile(r'(\b\w+\W+)(\1{3,})')
    return re_wrep.sub(_replace_wrep, t)


def fix_html(x:str) -> str:
    "List of replacements from html strings in `x`."
    re1 = re.compile(r'  +')
    x = x.replace('#39;', "'").replace('amp;', '&').replace('#146;', "'").replace(
        'nbsp;', ' ').replace('#36;', '$').replace('\\n', "\n").replace('quot;', "'").replace(
        '<br />', "\n").replace('\\"', '"').replace('<unk>',UNK).replace(' @.@ ','.').replace(
        ' @-@ ','-').replace(' @,@ ',',').replace('\\', ' \\ ')
    return re1.sub(' ', html.unescape(x))


def replace_all_caps(x:Collection[str]) -> Collection[str]:
    "Replace tokens in ALL CAPS in `x` by their lower version and add `TK_UP` before."
    res = []
    for t in x:
        if t.isupper() and len(t) > 1: res.append(TK_UP); res.append(t.lower())
        else: res.append(t)
    return res


def deal_caps(x:Collection[str]) -> Collection[str]:
    "Replace all Capitalized tokens in `x` by their lower version and add `TK_MAJ` before."
    res = []
    for t in x:
        if t == '': continue
        if t[0].isupper() and len(t) > 1 and t[1:].islower(): res.append(TK_MAJ)
        res.append(t.lower())
    return res

defaults.text_pre_rules = [fix_html, replace_rep, replace_wrep, spec_add_spaces, rm_useless_spaces]
defaults.text_post_rules = [replace_all_caps, deal_caps]


class Tokenizer():
    "Put together rules and a tokenizer function to tokenize text with multiprocessing."
    def __init__(self, tok_func:Callable=SpacyTokenizer, lang:str='en', pre_rules:ListRules=None,
                 post_rules:ListRules=None, special_cases:Collection[str]=None, n_cpus:int=None):
        self.tok_func,self.lang,self.special_cases = tok_func,lang,special_cases
        self.pre_rules  = ifnone(pre_rules,  defaults.text_pre_rules )
        self.post_rules = ifnone(post_rules, defaults.text_post_rules)
        self.special_cases = special_cases if special_cases is not None else defaults.text_spec_tok
        self.n_cpus = ifnone(n_cpus, defaults.cpus)

    def __repr__(self) -> str:
        res = f'Tokenizer {self.tok_func.__name__} in {self.lang} with the following rules:\n'
        for rule in self.pre_rules: res += f' - {rule.__name__}\n'
        for rule in self.post_rules: res += f' - {rule.__name__}\n'
        return res

    def process_text(self, t:str, tok:BaseTokenizer) -> List[str]:
        "Process one text `t` with tokenizer `tok`."
        for rule in self.pre_rules: t = rule(t)
        toks = tok.tokenizer(t)
        for rule in self.post_rules: toks = rule(toks)
        return toks

    def _process_all_1(self, texts:Collection[str]) -> List[List[str]]:
        "Process a list of `texts` in one process."
        tok = self.tok_func(self.lang)
        if self.special_cases: tok.add_special_cases(self.special_cases)
        return [self.process_text(str(t), tok) for t in texts]

    def process_all(self, texts:Collection[str]) -> List[List[str]]:
        "Process a list of `texts`."
        if self.n_cpus <= 1: return self._process_all_1(texts)
        with ProcessPoolExecutor(self.n_cpus) as e:
            return sum(e.map(self._process_all_1, partition_by_cores(texts, self.n_cpus)), [])


class Vocab():
    "Contain the correspondence between numbers and tokens and numericalize."
    def __init__(self, itos:Collection[str]):
        self.itos = itos
        self.stoi = defaultdict(int,{v:k for k,v in enumerate(self.itos)})

    def numericalize(self, t:Collection[str]) -> List[int]:
        "Convert a list of tokens `t` to their ids."
        return [self.stoi[w] for w in t]

    def textify(self, nums:Collection[int], sep=' ') -> List[str]:
        "Convert a list of `nums` to their tokens."
        return sep.join([self.itos[i] for i in nums]) if sep is not None else [self.itos[i] for i in nums] # type: ignore

    def __getstate__(self):
        return {'itos':self.itos}

    def __setstate__(self, state:dict):
        self.itos = state['itos']
        self.stoi = defaultdict(int,{v:k for k,v in enumerate(self.itos)})

    def save(self, path):
        "Save `self.itos` in `path`"
        pickle.dump(self.itos, open(path, 'wb'))

    @classmethod
    def create(cls, tokens:Tokens, max_vocab:int, min_freq:int) -> 'Vocab':
        "Create a vocabulary from a set of `tokens`."
        freq = Counter(p for o in tokens for p in o)
        itos = [o for o,c in freq.most_common(max_vocab) if c >= min_freq]
        for o in reversed(defaults.text_spec_tok):
            if o in itos: itos.remove(o)
            itos.insert(0, o)
        itos = itos[:max_vocab]
        if len(itos) < max_vocab: #Make sure vocab size is a multiple of 8 for fast mixed precision training
            while len(itos)%8 !=0: itos.append('xxfake')
        return cls(itos)

    @classmethod
    def load(cls, path):
        "Load the `Vocab` contained in `path`"
        itos = pickle.load(open(path, 'rb'))
        return cls(itos)