laywerrobot/lib/python3.6/site-packages/sklearn/datasets/twenty_newsgroups.py
2020-08-27 21:55:39 +02:00

372 lines
14 KiB
Python

"""Caching loader for the 20 newsgroups text classification dataset
The description of the dataset is available on the official website at:
http://people.csail.mit.edu/jrennie/20Newsgroups/
Quoting the introduction:
The 20 Newsgroups data set is a collection of approximately 20,000
newsgroup documents, partitioned (nearly) evenly across 20 different
newsgroups. To the best of my knowledge, it was originally collected
by Ken Lang, probably for his Newsweeder: Learning to filter netnews
paper, though he does not explicitly mention this collection. The 20
newsgroups collection has become a popular data set for experiments
in text applications of machine learning techniques, such as text
classification and text clustering.
This dataset loader will download the recommended "by date" variant of the
dataset and which features a point in time split between the train and
test sets. The compressed dataset size is around 14 Mb compressed. Once
uncompressed the train set is 52 MB and the test set is 34 MB.
The data is downloaded, extracted and cached in the '~/scikit_learn_data'
folder.
The `fetch_20newsgroups` function will not vectorize the data into numpy
arrays but the dataset lists the filenames of the posts and their categories
as target labels.
The `fetch_20newsgroups_vectorized` function will in addition do a simple
tf-idf vectorization step.
"""
# Copyright (c) 2011 Olivier Grisel <olivier.grisel@ensta.org>
# License: BSD 3 clause
import os
import logging
import tarfile
import pickle
import shutil
import re
import codecs
import numpy as np
import scipy.sparse as sp
from .base import get_data_home
from .base import load_files
from .base import _pkl_filepath
from .base import _fetch_remote
from .base import RemoteFileMetadata
from ..utils import check_random_state, Bunch
from ..feature_extraction.text import CountVectorizer
from ..preprocessing import normalize
from ..externals import joblib
logger = logging.getLogger(__name__)
# The original data can be found at:
# http://people.csail.mit.edu/jrennie/20Newsgroups/20news-bydate.tar.gz
ARCHIVE = RemoteFileMetadata(
filename='20news-bydate.tar.gz',
url='https://ndownloader.figshare.com/files/5975967',
checksum=('8f1b2514ca22a5ade8fbb9cfa5727df9'
'5fa587f4c87b786e15c759fa66d95610'))
CACHE_NAME = "20news-bydate.pkz"
TRAIN_FOLDER = "20news-bydate-train"
TEST_FOLDER = "20news-bydate-test"
def download_20newsgroups(target_dir, cache_path):
"""Download the 20 newsgroups data and stored it as a zipped pickle."""
train_path = os.path.join(target_dir, TRAIN_FOLDER)
test_path = os.path.join(target_dir, TEST_FOLDER)
if not os.path.exists(target_dir):
os.makedirs(target_dir)
logger.info("Downloading dataset from %s (14 MB)", ARCHIVE.url)
archive_path = _fetch_remote(ARCHIVE, dirname=target_dir)
logger.debug("Decompressing %s", archive_path)
tarfile.open(archive_path, "r:gz").extractall(path=target_dir)
os.remove(archive_path)
# Store a zipped pickle
cache = dict(train=load_files(train_path, encoding='latin1'),
test=load_files(test_path, encoding='latin1'))
compressed_content = codecs.encode(pickle.dumps(cache), 'zlib_codec')
with open(cache_path, 'wb') as f:
f.write(compressed_content)
shutil.rmtree(target_dir)
return cache
def strip_newsgroup_header(text):
"""
Given text in "news" format, strip the headers, by removing everything
before the first blank line.
"""
_before, _blankline, after = text.partition('\n\n')
return after
_QUOTE_RE = re.compile(r'(writes in|writes:|wrote:|says:|said:'
r'|^In article|^Quoted from|^\||^>)')
def strip_newsgroup_quoting(text):
"""
Given text in "news" format, strip lines beginning with the quote
characters > or |, plus lines that often introduce a quoted section
(for example, because they contain the string 'writes:'.)
"""
good_lines = [line for line in text.split('\n')
if not _QUOTE_RE.search(line)]
return '\n'.join(good_lines)
def strip_newsgroup_footer(text):
"""
Given text in "news" format, attempt to remove a signature block.
As a rough heuristic, we assume that signatures are set apart by either
a blank line or a line made of hyphens, and that it is the last such line
in the file (disregarding blank lines at the end).
"""
lines = text.strip().split('\n')
for line_num in range(len(lines) - 1, -1, -1):
line = lines[line_num]
if line.strip().strip('-') == '':
break
if line_num > 0:
return '\n'.join(lines[:line_num])
else:
return text
def fetch_20newsgroups(data_home=None, subset='train', categories=None,
shuffle=True, random_state=42,
remove=(),
download_if_missing=True):
"""Load the filenames and data from the 20 newsgroups dataset.
Read more in the :ref:`User Guide <20newsgroups>`.
Parameters
----------
data_home : optional, default: None
Specify a download and cache folder for the datasets. If None,
all scikit-learn data is stored in '~/scikit_learn_data' subfolders.
subset : 'train' or 'test', 'all', optional
Select the dataset to load: 'train' for the training set, 'test'
for the test set, 'all' for both, with shuffled ordering.
categories : None or collection of string or unicode
If None (default), load all the categories.
If not None, list of category names to load (other categories
ignored).
shuffle : bool, optional
Whether or not to shuffle the data: might be important for models that
make the assumption that the samples are independent and identically
distributed (i.i.d.), such as stochastic gradient descent.
random_state : numpy random number generator or seed integer
Used to shuffle the dataset.
remove : tuple
May contain any subset of ('headers', 'footers', 'quotes'). Each of
these are kinds of text that will be detected and removed from the
newsgroup posts, preventing classifiers from overfitting on
metadata.
'headers' removes newsgroup headers, 'footers' removes blocks at the
ends of posts that look like signatures, and 'quotes' removes lines
that appear to be quoting another post.
'headers' follows an exact standard; the other filters are not always
correct.
download_if_missing : optional, True by default
If False, raise an IOError if the data is not locally available
instead of trying to download the data from the source site.
"""
data_home = get_data_home(data_home=data_home)
cache_path = _pkl_filepath(data_home, CACHE_NAME)
twenty_home = os.path.join(data_home, "20news_home")
cache = None
if os.path.exists(cache_path):
try:
with open(cache_path, 'rb') as f:
compressed_content = f.read()
uncompressed_content = codecs.decode(
compressed_content, 'zlib_codec')
cache = pickle.loads(uncompressed_content)
except Exception as e:
print(80 * '_')
print('Cache loading failed')
print(80 * '_')
print(e)
if cache is None:
if download_if_missing:
logger.info("Downloading 20news dataset. "
"This may take a few minutes.")
cache = download_20newsgroups(target_dir=twenty_home,
cache_path=cache_path)
else:
raise IOError('20Newsgroups dataset not found')
if subset in ('train', 'test'):
data = cache[subset]
elif subset == 'all':
data_lst = list()
target = list()
filenames = list()
for subset in ('train', 'test'):
data = cache[subset]
data_lst.extend(data.data)
target.extend(data.target)
filenames.extend(data.filenames)
data.data = data_lst
data.target = np.array(target)
data.filenames = np.array(filenames)
else:
raise ValueError(
"subset can only be 'train', 'test' or 'all', got '%s'" % subset)
data.description = 'the 20 newsgroups by date dataset'
if 'headers' in remove:
data.data = [strip_newsgroup_header(text) for text in data.data]
if 'footers' in remove:
data.data = [strip_newsgroup_footer(text) for text in data.data]
if 'quotes' in remove:
data.data = [strip_newsgroup_quoting(text) for text in data.data]
if categories is not None:
labels = [(data.target_names.index(cat), cat) for cat in categories]
# Sort the categories to have the ordering of the labels
labels.sort()
labels, categories = zip(*labels)
mask = np.in1d(data.target, labels)
data.filenames = data.filenames[mask]
data.target = data.target[mask]
# searchsorted to have continuous labels
data.target = np.searchsorted(labels, data.target)
data.target_names = list(categories)
# Use an object array to shuffle: avoids memory copy
data_lst = np.array(data.data, dtype=object)
data_lst = data_lst[mask]
data.data = data_lst.tolist()
if shuffle:
random_state = check_random_state(random_state)
indices = np.arange(data.target.shape[0])
random_state.shuffle(indices)
data.filenames = data.filenames[indices]
data.target = data.target[indices]
# Use an object array to shuffle: avoids memory copy
data_lst = np.array(data.data, dtype=object)
data_lst = data_lst[indices]
data.data = data_lst.tolist()
return data
def fetch_20newsgroups_vectorized(subset="train", remove=(), data_home=None,
download_if_missing=True):
"""Load the 20 newsgroups dataset and transform it into tf-idf vectors.
This is a convenience function; the tf-idf transformation is done using the
default settings for `sklearn.feature_extraction.text.Vectorizer`. For more
advanced usage (stopword filtering, n-gram extraction, etc.), combine
fetch_20newsgroups with a custom `Vectorizer` or `CountVectorizer`.
Read more in the :ref:`User Guide <20newsgroups>`.
Parameters
----------
subset : 'train' or 'test', 'all', optional
Select the dataset to load: 'train' for the training set, 'test'
for the test set, 'all' for both, with shuffled ordering.
remove : tuple
May contain any subset of ('headers', 'footers', 'quotes'). Each of
these are kinds of text that will be detected and removed from the
newsgroup posts, preventing classifiers from overfitting on
metadata.
'headers' removes newsgroup headers, 'footers' removes blocks at the
ends of posts that look like signatures, and 'quotes' removes lines
that appear to be quoting another post.
data_home : optional, default: None
Specify an download and cache folder for the datasets. If None,
all scikit-learn data is stored in '~/scikit_learn_data' subfolders.
download_if_missing : optional, True by default
If False, raise an IOError if the data is not locally available
instead of trying to download the data from the source site.
Returns
-------
bunch : Bunch object
bunch.data: sparse matrix, shape [n_samples, n_features]
bunch.target: array, shape [n_samples]
bunch.target_names: list, length [n_classes]
"""
data_home = get_data_home(data_home=data_home)
filebase = '20newsgroup_vectorized'
if remove:
filebase += 'remove-' + ('-'.join(remove))
target_file = _pkl_filepath(data_home, filebase + ".pkl")
# we shuffle but use a fixed seed for the memoization
data_train = fetch_20newsgroups(data_home=data_home,
subset='train',
categories=None,
shuffle=True,
random_state=12,
remove=remove,
download_if_missing=download_if_missing)
data_test = fetch_20newsgroups(data_home=data_home,
subset='test',
categories=None,
shuffle=True,
random_state=12,
remove=remove,
download_if_missing=download_if_missing)
if os.path.exists(target_file):
X_train, X_test = joblib.load(target_file)
else:
vectorizer = CountVectorizer(dtype=np.int16)
X_train = vectorizer.fit_transform(data_train.data).tocsr()
X_test = vectorizer.transform(data_test.data).tocsr()
joblib.dump((X_train, X_test), target_file, compress=9)
# the data is stored as int16 for compactness
# but normalize needs floats
X_train = X_train.astype(np.float64)
X_test = X_test.astype(np.float64)
normalize(X_train, copy=False)
normalize(X_test, copy=False)
target_names = data_train.target_names
if subset == "train":
data = X_train
target = data_train.target
elif subset == "test":
data = X_test
target = data_test.target
elif subset == "all":
data = sp.vstack((X_train, X_test)).tocsr()
target = np.concatenate((data_train.target, data_test.target))
else:
raise ValueError("%r is not a valid subset: should be one of "
"['train', 'test', 'all']" % subset)
return Bunch(data=data, target=target, target_names=target_names)