Source code for

# coding: utf-8

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"""Utility classes and functions. They help organize and keep statistics of datasets."""
from __future__ import absolute_import
from __future__ import print_function

__all__ = ['Counter', 'count_tokens', 'concat_sequence', 'slice_sequence', 'train_valid_split']

import os
import collections
import zipfile
import tarfile
import numpy as np

from import SimpleDataset
from mxnet.gluon.utils import _get_repo_url, download, check_sha1

from .. import _constants as C

[docs]class Counter(collections.Counter): # pylint: disable=abstract-method """Counter class for keeping token frequencies."""
[docs] def discard(self, min_freq, unknown_token): """Discards tokens with frequency below min_frequency and represents them as `unknown_token`. Parameters ---------- min_freq: int Tokens whose frequency is under min_freq is counted as `unknown_token` in the Counter returned. unknown_token: str The representation for any unknown token. Returns ------- The Counter instance. Examples -------- >>> a = Counter({'a': 10, 'b': 1, 'c': 1}) >>> a.discard(3, '<unk>') Counter({'a': 10, '<unk>': 2}) """ freq = 0 ret = Counter({}) for token, count in self.items(): if count < min_freq: freq += count else: ret[token] = count ret[unknown_token] = ret.get(unknown_token, 0) + freq return ret
class DefaultLookupDict(dict): """Dictionary class with fall-back look-up with default value set in the constructor.""" def __init__(self, default, d=None): if d: super(DefaultLookupDict, self).__init__(d) else: super(DefaultLookupDict, self).__init__() self._default = default def __getitem__(self, k): return self.get(k, self._default)
[docs]def count_tokens(tokens, to_lower=False, counter=None): r"""Counts tokens in the specified string. For token_delim='(td)' and seq_delim='(sd)', a specified string of two sequences of tokens may look like:: (td)token1(td)token2(td)token3(td)(sd)(td)token4(td)token5(td)(sd) Parameters ---------- tokens : list of str A source list of tokens. to_lower : bool, default False Whether to convert the source source_str to the lower case. counter : Counter or None, default None The Counter instance to be updated with the counts of `tokens`. If None, return a new Counter instance counting tokens from `tokens`. Returns ------- The `counter` Counter instance after being updated with the token counts of `source_str`. If `counter` is None, return a new Counter instance counting tokens from `source_str`. Examples -------- >>> source_str = ' Life is great ! \\n life is good . \\n' >>> source_str_tokens = filter(None, re.split(' |\n', source_str)) >>> count_tokens(source_str_tokens) Counter({'!': 1, '.': 1, 'good': 1, 'great': 1, 'is': 2, 'life': 2}) """ if to_lower: tokens = [t.lower() for t in tokens] if counter is None: return Counter(tokens) else: counter.update(tokens) return counter
[docs]def concat_sequence(sequences): """Concatenate sequences of tokens into a single flattened list of tokens. Parameters ---------- sequences : list of list of object Sequences of tokens, each of which is an iterable of tokens. Returns ------- Flattened list of tokens. """ return [token for seq in sequences for token in seq if token]
[docs]def slice_sequence(sequence, length, pad_last=False, pad_val=C.PAD_TOKEN, overlap=0): """Slice a flat sequence of tokens into sequences tokens, with each inner sequence's length equal to the specified `length`, taking into account the requested sequence overlap. Parameters ---------- sequence : list of object A flat list of tokens. length : int The length of each of the samples. pad_last : bool, default False Whether to pad the last sequence when its length doesn't align. If the last sequence's length doesn't align and ``pad_last`` is False, it will be dropped. pad_val : object, default The padding value to use when the padding of the last sequence is enabled. In general, the type of ``pad_val`` should be the same as the tokens. overlap : int, default 0 The extra number of items in current sample that should overlap with the next sample. Returns ------- List of list of tokens, with the length of each inner list equal to `length`. """ if length <= overlap: raise ValueError('length needs to be larger than overlap') if pad_last: pad_len = _slice_pad_length(len(sequence), length, overlap) sequence = sequence + [pad_val] * pad_len num_samples = (len(sequence)-length) // (length-overlap) + 1 return [sequence[i*(length-overlap):((i+1)*length-i*overlap)] for i in range(num_samples)]
def _slice_pad_length(num_items, length, overlap=0): """Calculate the padding length needed for sliced samples in order not to discard data. Parameters ---------- num_items : int Number of items in dataset before collating. length : int The length of each of the samples. overlap : int, default 0 The extra number of items in current sample that should overlap with the next sample. Returns ------- Length of paddings. """ if length <= overlap: raise ValueError('length needs to be larger than overlap') step = length-overlap span = num_items-length residual = span % step if residual: return step - residual else: return 0 _vocab_sha1 = {'wikitext-2': 'be36dc5238c2e7d69720881647ab72eb506d0131', 'gbw': 'b3e832155eb66018b8dfe0b77c00b498c29bed67'} _url_format = '{repo_url}gluon/dataset/vocab/{file_name}.zip'
[docs]def train_valid_split(dataset, valid_ratio=0.05): """Split the dataset into training and validation sets. Parameters ---------- train : list A list of training samples. valid_ratio : float, default 0.05 Proportion of training samples to use for validation set range: [0, 1] Returns ------- train : SimpleDataset valid : SimpleDataset """ if not 0.0 <= valid_ratio <= 1.0: raise ValueError('valid_ratio should be in [0, 1]') num_train = len(dataset) num_valid = np.ceil(num_train * valid_ratio).astype('int') indices = np.arange(num_train) np.random.shuffle(indices) valid = SimpleDataset([dataset[indices[i]] for i in range(num_valid)]) train = SimpleDataset([dataset[indices[i + num_valid]] for i in range(num_train - num_valid)]) return train, valid
def short_hash(name): if name not in _vocab_sha1: raise ValueError('Vocabulary for {name} is not available.'.format(name=name)) return _vocab_sha1[name][:8] def _load_pretrained_vocab(name, root=os.path.join('~', '.mxnet', 'models')): """Load the accompanying vocabulary object for pretrained model. Parameters ---------- name : str Name of the vocabulary, usually the name of the dataset. root : str, default '~/.mxnet/models' Location for keeping the model parameters. Returns ------- Vocab Loaded vocabulary object for the pretrained model. """ file_name = '{name}-{short_hash}'.format(name=name, short_hash=short_hash(name)) root = os.path.expanduser(root) file_path = os.path.join(root, file_name+'.vocab') sha1_hash = _vocab_sha1[name] if os.path.exists(file_path): if check_sha1(file_path, sha1_hash): return _load_vocab_file(file_path) else: print('Detected mismatch in the content of model vocab file. Downloading again.') else: print('Vocab file is not found. Downloading.') if not os.path.exists(root): os.makedirs(root) zip_file_path = os.path.join(root, file_name+'.zip') repo_url = _get_repo_url() if repo_url[-1] != '/': repo_url = repo_url + '/' download(_url_format.format(repo_url=repo_url, file_name=file_name), path=zip_file_path, overwrite=True) with zipfile.ZipFile(zip_file_path) as zf: zf.extractall(root) os.remove(zip_file_path) if check_sha1(file_path, sha1_hash): return _load_vocab_file(file_path) else: raise ValueError('Downloaded file has different hash. Please try again.') def _load_vocab_file(file_path): with open(file_path, 'r') as f: from ..vocab import Vocab return Vocab.from_json( def _get_home_dir(): """Get home directory for storing datasets/models/pre-trained word embeddings""" _home_dir = os.environ.get('MXNET_HOME', os.path.join('~', '.mxnet')) # expand ~ to actual path _home_dir = os.path.expanduser(_home_dir) return _home_dir def _extract_archive(file, target_dir): """Extract archive file Parameters ---------- file : str Absolute path of the archive file. target_dir : str Target directory of the archive to be uncompressed """ if file.endswith('.gz') or file.endswith('.tar') or file.endswith('.tgz'): archive =, 'r') elif file.endswith('.zip'): archive = zipfile.ZipFile(file, 'r') else: raise Exception('Unrecognized file type: ' + file) archive.extractall(path=target_dir) archive.close()