一、BERT文本分类实战
BERT是一种语言模型,可以用于语言推理、问答和分类等任务。在文本分类任务中,BERT可以作为一个预训练模型来提高分类准确性。为了使用BERT进行文本分类,我们需要做以下几步:
1、从Hugging Face的transformers库中加载预训练的BERT模型并进行微调。
2、对原始文本进行编码,并在输入层添加一些处理。
3、在输入层之后添加一些全连接层来进行分类。
# 加载预训练的BERT模型 from transformers import BertForSequenceClassification model = BertForSequenceClassification.from_pretrained("bert-base-uncased") # 对原始文本进行编码并添加处理 inputs = tokenizer.encode_plus(text, max_length=512, truncation=True, padding='max_length', add_special_tokens=True, return_token_type_ids=False, return_attention_mask=True, return_tensors='pt') # 添加全连接层来进行分类 from torch import nn class SentimentClassifier(nn.Module): def __init__(self, n_classes): super(SentimentClassifier, self).__init__() self.bert = BertForSequenceClassification.from_pretrained("bert-base-uncased") self.dropout = nn.Dropout(0.3) self.out = nn.Linear(768, n_classes) def forward(self, input_ids, attention_mask): _, pooled_output = self.bert(input_ids=input_ids, attention_mask=attention_mask, return_dict=False) output = self.dropout(pooled_output) return self.out(output)
二、BERT文本分类使用全连接层
BERT在语言理解方面表现突出,但在分类任务中,我们仍需要添加额外的分类层。这里我们可以使用全连接层来进行分类。全连接层将BERT模型的输出与标签进行比较,以确定输入应该归类到哪个类别。
全连接层的实现包括两个步骤:首先,需要将BERT的输出向量送入全连接层中,并添加一个激活函数。然后,需要将全连接层的输出向量与标签进行比较。
from torch import nn class SentimentClassifier(nn.Module): def __init__(self, n_classes): super(SentimentClassifier, self).__init__() self.bert = BertModel.from_pretrained('bert-base-uncased') self.dropout = nn.Dropout(0.3) self.out = nn.Linear(768, n_classes) def forward(self, input_ids, attention_mask): _, pooled_output = self.bert(input_ids=input_ids, attention_mask=attention_mask, return_dict=False) output = self.dropout(pooled_output) return self.out(output)
三、BERT文本分类 PyTorch
在PyTorch中使用BERT进行文本分类任务的过程可以分为以下五个步骤:
1、加载预训练的BERT模型。
2、在输入层添加一些处理,并将该层的输出送入BERT模型。
3、将BERT模型的输出向量送入全连接层中。
4、计算损失并进行反向传播。
5、使用优化器更新模型参数。
from transformers import BertTokenizer, BertForSequenceClassification, AdamW tokenizer = BertTokenizer.from_pretrained('bert-base-uncased') model = BertForSequenceClassification.from_pretrained('bert-base-uncased') optimizer = AdamW(model.parameters(), lr=2e-5, eps=1e-8) loss_fn = nn.CrossEntropyLoss() device = torch.device("cuda" if torch.cuda.is_available() else "cpu") model.to(device) def train(epoch): model.train() for step, batch in enumerate(train_dataloader): input_ids = batch[0].to(device) attention_mask = batch[1].to(device) labels = batch[2].to(device) model.zero_grad() output = model(input_ids=input_ids, attention_mask=attention_mask, labels=labels) loss = output.loss loss.backward() optimizer.step() def test(): model.eval() total_correct = 0 total_samples = 0 with torch.no_grad(): for step, batch in enumerate(val_dataloader): input_ids = batch[0].to(device) attention_mask = batch[1].to(device) labels = batch[2].to(device) output = model(input_ids=input_ids, attention_mask=attention_mask) predictions = torch.argmax(output.logits, dim=1) total_correct += torch.sum(predictions == labels) total_samples += predictions.shape[0] accuracy = float(total_correct) / float(total_samples) print("Accuracy: {0:.2%}".format(accuracy))
四、BERT文本分类代码
下面是BERT文本分类的完整代码,包括数据预处理、模型训练和测试。
import pandas as pd import numpy as np import torch from torch.utils.data import DataLoader, TensorDataset, random_split from transformers import BertTokenizer, BertForSequenceClassification, AdamW def get_data_loader(): df = pd.read_csv('data.csv') # 将数据集标签映射为数字 label_map = {'positive': 2, 'neutral': 1, 'negative': 0} df = df.replace({'label': label_map}) # 加载BERT tokenizer tokenizer = BertTokenizer.from_pretrained('bert-base-uncased', do_lower_case=True) # 将文本数据编码为token input_ids = [] attention_masks = [] for text in df.text: encoded_dict = tokenizer.encode_plus(text, add_special_tokens=True, max_length=64, padding='max_length', return_attention_mask=True, return_tensors='pt') input_ids.append(encoded_dict['input_ids']) attention_masks.append(encoded_dict['attention_mask']) labels = torch.tensor(df.label) dataset = TensorDataset(torch.cat(input_ids, dim=0), torch.cat(attention_masks, dim=0), labels) train_size = int(0.8 * len(dataset)) val_size = len(dataset) - train_size train_data, val_data = random_split(dataset, [train_size, val_size]) batch_size = 32 train_dataloader = DataLoader(train_data, sampler=None, batch_size=batch_size) val_dataloader = DataLoader(val_data, sampler=None, batch_size=batch_size) return train_dataloader, val_dataloader def train(epoch): model.train() for step, batch in enumerate(train_dataloader): input_ids = batch[0].to(device) attention_mask = batch[1].to(device) labels = batch[2].to(device) model.zero_grad() output = model(input_ids=input_ids, attention_mask=attention_mask, labels=labels) loss = output.loss loss.backward() optimizer.step() def test(): model.eval() total_correct = 0 total_samples = 0 with torch.no_grad(): for step, batch in enumerate(val_dataloader): input_ids = batch[0].to(device) attention_mask = batch[1].to(device) labels = batch[2].to(device) output = model(input_ids=input_ids, attention_mask=attention_mask) predictions = torch.argmax(output.logits, dim=1) total_correct += torch.sum(predictions == labels) total_samples += predictions.shape[0] accuracy = float(total_correct) / float(total_samples) print("Accuracy: {0:.2%}".format(accuracy)) # 获取数据集,并将模型转移到GPU上 train_dataloader, val_dataloader = get_data_loader() device = torch.device("cuda" if torch.cuda.is_available() else "cpu") # 加载BERT模型和优化器 model = BertForSequenceClassification.from_pretrained('bert-base-uncased', num_labels=3, output_attentions=False, output_hidden_states=False) model.to(device) optimizer = AdamW(model.parameters(), lr=2e-5, eps=1e-8) # 训练模型 for epoch in range(10): train(epoch) # 测试模型 test()
五、BERT文本分类输入
在使用BERT进行文本分类之前,我们需要先对原始文本进行处理,以确保其能够被BERT模型接受。
# 加载BERT tokenizer tokenizer = BertTokenizer.from_pretrained('bert-base-uncased', do_lower_case=True) # 将文本数据编码为token text = 'This is a sample sentence' encoded_dict = tokenizer.encode_plus(text, add_special_tokens=True, max_length=64, padding='max_length', return_attention_mask=True, return_tensors='pt') input_ids = encoded_dict['input_ids'] attention_mask = encoded_dict['attention_mask']
六、BERT文本分类数据预处理
数据预处理是使用BERT进行文本分类的重要步骤。在BERT模型中,输入需要经过一些预处理以保证模型的准确性。
在进行数据预处理时,我们需要:
1、将文本数据标记化:在这个过程中,我们将文本分割成单词,并将每个单词分配一个唯一的标识符。
2、将标记化的数据转换为BERT模型的输入格式:BERT初始化输入是向量,因此我们需要对标记进行向量化处理。
3、将输入向量传递给BERT模型进行分类。
# 示例:将Stanford Sentiment Treebank数据集加载到dataframe中,并对标签进行编码 import pandas as pd df = pd.read_csv('/path/to/data.tsv', sep='\t') label_map = {'positive': 2, 'neutral': 1, 'negative': 0} df = df.replace({'label': label_map}) # 加载BERT tokenizer,对数据集进行标记化 tokenizer = BertTokenizer.from_pretrained('bert-base-uncased', do_lower_case=True) input_ids = [] attention_masks = [] for text in df.text: encoded_dict = tokenizer.encode_plus(text, add_special_tokens=True, max_length=64, padding='max_length', return_attention_mask=True, return_tensors='pt') input_ids.append(encoded_dict['input_ids']) attention_masks.append(encoded_dict['attention_mask']) labels = torch.tensor(df.label) # 将标记化的数据集转换为Tensor,可以用于PyTorch模型训练。 dataset = TensorDataset(torch.cat(input_ids, dim=0), torch.cat(attention_masks, dim=0), labels)
七、BERT文本分类参考文献
以下是一些参考资料,可以帮助你更深入地了解BERT在文本分类任务中的应用:
1、BERT for Text Classification:https://towardsdatascience.com/bert-for-text-classification-2c2aafa8b5a5
2、Training Sentiment Analysis Model:https://towardsdatascience.com/building-a-sentiment-analysis-model-from-scratch-4b67668912e3
3、Fine-tuning BERT for Sentiment Analysis:https://medium.com/swlh/fine-tuning-bert-for-sentiment-analysis-73f6a6374d6d
八、BERT文本分类tensorflow
与PyTorch类似,TensorFlow也可以使用BERT进行文本分类任务的处理。以下是使用TensorFlow实现BERT文本分类的示例代码:
import tensorflow as tf from transformers import TFBertModel from transformers import BertTokenizer # 加载BERT tokenizer tokenizer = BertTokenizer.from_pretrained('bert-base-uncased') # 加载预训练的BERT模型 bert = TFBertModel.from_pretrained('bert-base-uncased') # 创建分类模型 class SentimentClassifier(tf.keras.Model): def __init__(self, num_labels): super(SentimentClassifier, self).__init__() self.bert = bert self.dropout = tf.keras.layers.Dropout(0.3) self.out = tf.keras.layers.Dense(num_labels, activation='softmax') def call(self, inputs, attention_mask=None, token_type_ids=None): outputs = self.bert(inputs, attention_mask=attention_mask, token_type_ids=token_type_ids) pooled_output = outputs[1] pooled_output = self.dropout(pooled_output) return self.out(pooled_output) # 训练模型 model = SentimentClassifier(num_labels=3) optimizer = tf.keras.optimizers.Adam(learning_rate=2e-5, epsilon=1e-08, clipnorm=1.0) loss_fn = tf.keras.losses.SparseCategoricalCrossentropy(from_logits=True) model.compile(optimizer=optimizer, loss=loss_fn, metrics=['accuracy']) model.fit(train_data, epochs=10, validation_data=val_data)