DataWhale-NLP理论基础和实践（进阶）-lixiaome

@TOCDataWhale-NLP理论基础和实践（进阶）-lixiaome

一、IMDB数据集下载和探索

import tensorflow as tf
from tensorflow import keras
import numpy as np
import os
import pandas as pd
imdb = keras.datasets.imdb

探索数据
查看数据整体情况

(train_data, train_labels), (test_data, test_labels) = imdb.load_data(num_words=10000)
print(len(train_data))
print(len(train_labels))
print(len(test_data))
print(len(test_labels))

查看单个句子情况
可发现每个句子长度不一致，神经网络中每个句子的长度相同，之后需要把句子喂进网络时需记得补足长度

#尝试查看前5句
for i in range(5):
	print(train_data[i])
	print(len(train_data[i]))

将数字转回单词

# 单词和数字的mapping字典
word_index = imdb.get_word_index()

# 每句前面留位置给pad等
word_index = {k:(v+3) for k,v in word_index.items()}
word_index["<PAD>"] = 0
word_index["<START>"] = 1
word_index["<UNK>"] = 2  # unknown
word_index["<UNUSED>"] = 3

reverse_word_index = dict([(value, key) for (key, value) in word_index.items()])

def decode_review(text):
    return ' '.join([reverse_word_index.get(i, '?') for i in text])

可以使用decode_review现实影评文本

for i in range(5):
	print(decode_review(train_data[i])

二、THUCNews数据集下载和探索

# coding: utf-8

import sys
from collections import Counter

import numpy as np
import tensorflow.keras as kr

if sys.version_info[0] > 2:
    is_py3 = True
else:
    reload(sys)
    sys.setdefaultencoding("utf-8")
    is_py3 = False


def native_word(word, encoding='utf-8'):
    """如果在python2下面使用python3训练的模型，可考虑调用此函数转化一下字符编码"""
    if not is_py3:
        return word.encode(encoding)
    else:
        return word


def native_content(content):
    if not is_py3:
        return content.decode('utf-8')
    else:
        return content


def open_file(filename, mode='r'):
    """
    常用文件操作，可在python2和python3间切换.
    mode: 'r' or 'w' for read or write
    """
    if is_py3:
        return open(filename, mode, encoding='utf-8', errors='ignore')
    else:
        return open(filename, mode)


def read_file(filename):
    """读取文件数据"""
    contents, labels = [], []
    with open_file(filename) as f:
        for line in f:
            try:
                label, content = line.strip().split('\t')
                if content:
                    contents.append(list(native_content(content)))
                    labels.append(native_content(label))
            except:
                pass
    return contents, labels


def build_vocab(train_dir, vocab_dir, vocab_size=5000):
    """根据训练集构建词汇表，存储"""
    data_train, _ = read_file(train_dir)

    all_data = []
    for content in data_train:
        all_data.extend(content)

    counter = Counter(all_data)
    count_pairs = counter.most_common(vocab_size - 1)
    words, _ = list(zip(*count_pairs))
    # 添加一个 <PAD> 来将所有文本pad为同一长度
    words = ['<PAD>'] + list(words)
    open_file(vocab_dir, mode='w').write('\n'.join(words) + '\n')


def read_vocab(vocab_dir):
    """读取词汇表"""
    # words = open_file(vocab_dir).read().strip().split('\n')
    with open_file(vocab_dir) as fp:
        # 如果是py2 则每个值都转化为unicode
        words = [native_content(_.strip()) for _ in fp.readlines()]
    word_to_id = dict(zip(words, range(len(words))))
    return words, word_to_id


def read_category():
    """读取分类目录，固定"""
    categories = ['体育', '财经', '房产', '家居', '教育', '科技', '时尚', '时政', '游戏', '娱乐']

    categories = [native_content(x) for x in categories]

    cat_to_id = dict(zip(categories, range(len(categories))))

    return categories, cat_to_id


def to_words(content, words):
    """将id表示的内容转换为文字"""
    return ''.join(words[x] for x in content)


def process_file(filename, word_to_id, cat_to_id, max_length=600):
    """将文件转换为id表示"""
    contents, labels = read_file(filename)

    data_id, label_id = [], []
    for i in range(len(contents)):
        data_id.append([word_to_id[x] for x in contents[i] if x in word_to_id])
        label_id.append(cat_to_id[labels[i]])

    # 使用keras提供的pad_sequences来将文本pad为固定长度
    x_pad = kr.preprocessing.sequence.pad_sequences(data_id, max_length)
    y_pad = kr.utils.to_categorical(label_id, num_classes=len(cat_to_id))  # 将标签转换为one-hot表示

    return x_pad, y_pad


def batch_iter(x, y, batch_size=64):
    """生成批次数据"""
    data_len = len(x)
    num_batch = int((data_len - 1) / batch_size) + 1

    indices = np.random.permutation(np.arange(data_len))
    x_shuffle = x[indices]
    y_shuffle = y[indices]

    for i in range(num_batch):
        start_id = i * batch_size
        end_id = min((i + 1) * batch_size, data_len)
        yield x_shuffle[start_id:end_id], y_shuffle[start_id:end_id]

三、学习召回率、准确率、ROC曲线、AUC、PR曲线这些基本概念
读西瓜书相关章节。