【神经网络与深度学习】文本情感分类

数据准备

AclImdb – v1 Dataset 是用于二进制情绪分类的大型电影评论数据集，其涵盖比基准数据集更多的数据，其中有 25,000 条电影评论用于训练，25,000 条用于测试，还有其他未经标记的数据可供使用。

数据预处理和数据装载

import refrom torch.utils.data import DataLoader
from torch.utils.data import Dataset
import osdef tokenization(content):content = re.sub("<.*?>"," ",content)fileters = ['\t','\n','\x97','\x96','#','%','$','&',"\.","\?","!","\,"]content = re.sub("|".join(fileters)," ",content)tokens = [i.strip().lower() for i in content.split()]return tokensdef collate_fn(batch):""":param batch:( [tokens, labels], [tokens, labels]):return:"""content, label  = list(zip(*batch))return content,labelclass ImdbDataset(Dataset):def __init__(self, train=True):self.train_data_path = '..\\aclImdb\\train\\'self.test_data_path = '..\\aclImdb\\test\\'data_path = self.train_data_path if train else self.test_data_path#把所有文件名放入列表temp_data_path = [os.path.join(data_path,"pos"), os.path.join(data_path+"neg")]print(temp_data_path)self.total_file_path = [] #所有评论文件路径for path in temp_data_path:file_name_list = os.listdir(path)file_path_list = [os.path.join(path, i) for i in file_name_list if i.endswith(".txt")]self.total_file_path.extend(file_path_list)def __len__(self):return len(self.total_file_path)def __getitem__(self, index):file_path = self.total_file_path[index]# 获取labellabelstr = file_path.split("\\")[-2]label = 0 if labelstr == "neg" else 1# 获取内容content = open(file_path).read()tokens = tokenization(content)return tokens, labeldef get_data(train=True):imbd_dataset = ImdbDataset(train)data_loader = DataLoader(imbd_dataset, batch_size=2, shuffle=True,collate_fn=collate_fn)return data_loader

文本序列化

把文本里每个词语和其对应数字，使用字典保存即句子—>数字列表
思路：

句子进行分词（tokenization)
词语存入字典，统计出现次数，根据出现次数对齐进行过滤
把文本转数字序列
把数字序列转文本

遇到新出现的字符再词典里没有，可以用特殊字符替代
预保持每个batch里的序列大小一致，使用填充方法

"""
构建词典 把句子转换成序列 再把序列转成句子
"""class Word2Sequence:UNK_TAG = "UNK"PAD_TAG = "PAD"UNK =0PAD =1def __init__(self):self.dict = {self.UNK_TAG: self.UNK,self.PAD_TAG: self.PAD}self.count = {}def fit(self, sentence):# 把单个句子保存到dictfor word in sentence:self.count[word] = self.count.get(word, 0)+1def build_vocab(self, min=5, max=None, max_features=None):""":param min::param max::param max_features: 一共保留多少个词语:return:"""# 删除count中词频小于min的词语self.count = {word:value for word, value in self.count.items() if value>min}# 删除count中词频大于max的词语if max is not None:self.count = {word: value for word, value in self.count.items() if value < max}# 限制保留的词语数if max_features is not None:temp = sorted(self.cout.items(), key=lambda x:x[-1], reverse=True)[:max_features]self.count = dict(temp)# 把 词语 ——>数字for word in self.count:self.dict[word] = len(self.dict)# 得到一个反转的dict字典self.inverse_dict = dict(zip(self.dict.values(), self.dict.keys()))def transform(self, sentence, max_len=None):"""把句子 转成 序列:param sentence:  [word1, word2, ..]:param max_len: 对句子进行填充或者裁剪:return:"""if max_len is not None:if max_len > len(sentence):sentence = sentence + [self.PAD_TAG] * (max_len - len(sentence)) # 填充if max_len < len(sentence):sentence = sentence[:max_len] # 裁剪return [self.dict.get(word, self.UNK) for word in sentence]def inverse_transform(self, indices):# 把 序列 ——>句子return [self.inverse_dict.get(idx) for idx in indices]if __name__ == '__main__':ws = Word2Sequence()ws.fit(["我","是","你","的","爸爸"])ws.fit(["我","是","我","的","人"])ws.build_vocab(min=0)print(ws.dict)re = ws.transform(["我","爱","人"],max_len=10)print(re)ret = ws.inverse_transform(re)print(ret)

模型构建（简单全连接）

注意 word_embedding的使用！

"""
定义模型
"""
import torch
import torch.nn as nn
import torch.nn.functional as F
from lib import ws,max_len
from dataset import get_data
class MyModel(nn.Module):def __init__(self):super(MyModel, self).__init__()self.embedding = nn.Embedding(len(ws), 100)self.fc = nn.Linear(100*max_len, 2)def forward(self, input):""":param input: [batch_size, max_len]:return:"""x = self.embedding(input) # [batch_size, max_len, 100]x = x.view([-1, 100*max_len])output = self.fc(x)return F.log_softmax(output,dim=-1)model = MyModel()
optimizer = torch.optim.Adam(model.parameters(),lr=0.001)
def train(epoch):for idx,(input,target) in enumerate(get_data(train=True)):# 梯度清零optimizer.zero_grad()output= model(input)loss = F.nll_loss(output,target)loss.backward()optimizer.step()print(loss.item())if __name__ == '__main__':for i in range(1):train(epoch=i)