ch8-Online-Sentiment-Analysis.py

import numpy as np
import re
from nltk.corpus import stopwords
stop = stopwords.words('english')

def tokenizer(text):
    text = re.sub('<[^>]*>', '', text)
    emoticons = re.findall('(?::|;|=)(?:-)?(?:\)|\(|D|P)',text.lower())
    text = re.sub('[\W]+', ' ', text.lower()) + ' '.join(emoticons).replace('-', '')
    tokenized = [w for w in text.split() if w not in stop]
    return tokenized


def stream_docs(path):
    with open(path, 'r', encoding='utf-8') as csv:
        next(csv) # skip header
        for line in csv:
            text, label = line[:-3], int(line[-2])
            yield text, label


def get_minibatch(doc_stream, size):
    docs, y = [], []
    try:
        for _ in range(size):
            text, label = next(doc_stream)
            docs.append(text)
            y.append(label)
    except StopIteration:
        return None, None

    return docs, y


from sklearn.feature_extraction.text import HashingVectorizer
from sklearn.linear_model import SGDClassifier

vect = HashingVectorizer(decode_error='ignore',
                          n_features=2**21,
                          preprocessor=None,
                          tokenizer=tokenizer)

# regularized linear models with stochastic gradient descent (SGD)
clf = SGDClassifier(loss='log', random_state=1, n_iter=1)
doc_stream = stream_docs(path='./movie_data.csv')

import pyprind
pbar = pyprind.ProgBar(45)
classes = np.array([0, 1])
for _ in range(45):
    X_train, y_train = get_minibatch(doc_stream, size=1000)
    if not X_train:
        break

    X_train = vect.transform(X_train)
    clf.partial_fit(X_train, y_train, classes=classes)
    pbar.update()


X_test, y_test = get_minibatch(doc_stream, size=5000)
X_test = vect.transform(X_test)
print('Accuracy: %.3f' % clf.score(X_test, y_test))

clf = clf.partial_fit(X_test, y_test)