✨做一次按NLP项目常见工具的使用拆解
1. tokenizer
from torchtext.data.utils import get_tokenizertokenizer = get_tokenizer('basic_english')
text_sample = "We're going on an adventure! The weather is really nice today."
tokens = tokenizer(text_sample)
print(tokens)['we', "'", 're', 'going', 'on', 'an', 'adventure', '!', 'the', 'weather', 'is', 'really', 'nice', 'today', '.']
2. vocab
from torchtext.vocab import build_vocab_from_iterator
from torchtext.data.utils import get_tokenizer# 创建分词器
tokenizer = get_tokenizer('basic_english')# 测试数据
test_sentences = ["The quick brown fox jumps over the lazy dog.","Hello world! This is a test for building vocabulary.",
]vocab = build_vocab_from_iterator((tokenizer(sentence) for sentence in test_sentences),specials=['<unk>', '<pad>'],min_freq=1 # 设置最小频率为1
)vocab.set_default_index(vocab['<unk>'])print("词表大小:", len(vocab))
print("'fox'的索引:", vocab['fox'])词表大小: 21
'fox'的索引: 10
3. Dataloader（示例1）
import torch
from torch.nn.utils.rnn import pad_sequence
from torch.utils.data import Dataset, DataLoader
from torchtext.vocab import build_vocab_from_iterator
from torchtext.data.utils import get_tokenizer# 1. 创建分词器
tokenizer = get_tokenizer('basic_english')# 2. 测试数据
train_sentences = ["The quick brown fox jumps over the lazy dog.","Hello world! This is a test for building vocabulary.",# 你可以在这里添加更多训练句子
]
test_sentences = ["The quick brown fox jumps over the lazy dog.","Hello world! This is a test for building vocabulary.",
]# 3. 构建词表
vocab = build_vocab_from_iterator((tokenizer(sentence) for sentence in train_sentences),specials=['<unk>', '<pad>'],min_freq=1
)
vocab.set_default_index(vocab['<unk>'])print("词表大小:", len(vocab))
print("'fox'的索引:", vocab['fox'])# 4. 自定义 Dataset
class TextDataset(Dataset):def __init__(self, sentences, vocab, tokenizer):self.sentences = sentencesself.vocab = vocabself.tokenizer = tokenizerdef __len__(self):return len(self.sentences)def __getitem__(self, idx):tokens = self.tokenizer(self.sentences[idx])indices = [self.vocab[token] for token in tokens]return torch.tensor(indices, dtype=torch.long)# 5. 创建 Dataset 实例
train_dataset = TextDataset(train_sentences, vocab, tokenizer)
test_dataset = TextDataset(test_sentences, vocab, tokenizer)# 6. DataLoader 与 Padding Collate 函数def collate_fn(batch):# batch 是一个 list of tensorsreturn pad_sequence(batch, batch_first=True, padding_value=vocab['<pad>'])train_loader = DataLoader(train_dataset, batch_size=2, shuffle=True, collate_fn=collate_fn)
test_loader = DataLoader(test_dataset, batch_size=2, shuffle=False, collate_fn=collate_fn)# 7. 测试 DataLoader 输出
print("\n=== Train Batch Indices ===")
for batch in train_loader:print(batch)breakprint("\n=== Test Batch Indices ===")
for batch in test_loader:print(batch)break
=== Train Batch Indices ===
tensor([[11, 20, 4, 18, 12, 5, 17, 9, 7, 19, 2],
[ 3, 16, 6, 10, 13, 15, 3, 14, 8, 2, 1]])=== Test Batch Indices ===
tensor([[ 3, 16, 6, 10, 13, 15, 3, 14, 8, 2, 1],
[11, 20, 4, 18, 12, 5, 17, 9, 7, 19, 2]])
4. Dataloader（示例2）
import torch
from torch.nn.utils.rnn import pad_sequence
from torch.utils.data import Dataset, DataLoader
from torchtext.vocab import build_vocab_from_iterator
from torchtext.data.utils import get_tokenizer# 1. 创建分词器
tokenizer = get_tokenizer('basic_english')# 2. 带标签的训练与测试数据 (句子, 标签)
train_data = [("The quick brown fox jumps over the lazy dog.", 1), # 正面情感("Hello world! This is a test for building vocabulary.", 0), # 负面情感# 可添加更多 (sentence, label)
]
test_data = [("The quick brown fox jumps over the lazy dog.", 1),("Hello world! This is a test for building vocabulary.", 0),
]# 3. 构建词表，只基于训练数据中的句子
vocab = build_vocab_from_iterator((tokenizer(sentence) for sentence, _ in train_data),specials=['<unk>', '<pad>'],min_freq=1
)
vocab.set_default_index(vocab['<unk>'])print("词表大小:", len(vocab))
print("'fox'的索引:", vocab['fox'])# 4. 自定义 Dataset，返回 (indices_tensor, label_tensor)
class TextDataset(Dataset):def __init__(self, data, vocab, tokenizer):self.data = dataself.vocab = vocabself.tokenizer = tokenizerdef __len__(self):return len(self.data)def __getitem__(self, idx):sentence, label = self.data[idx]tokens = self.tokenizer(sentence)indices = [self.vocab[token] for token in tokens]return torch.tensor(indices, dtype=torch.long), torch.tensor(label, dtype=torch.long)# 5. Padding 与 collate_fn
def collate_fn(batch):sequences, labels = zip(*batch)padded_seqs = pad_sequence(sequences, batch_first=True, padding_value=vocab['<pad>'])labels_tensor = torch.stack(labels)return padded_seqs, labels_tensor# 6. 创建 DataLoader
train_dataset = TextDataset(train_data, vocab, tokenizer)
test_dataset = TextDataset(test_data, vocab, tokenizer)train_loader = DataLoader(train_dataset, batch_size=2, shuffle=True, collate_fn=collate_fn
)
test_loader = DataLoader(test_dataset, batch_size=2, shuffle=False, collate_fn=collate_fn
)# 7. 测试输出
print("\n=== Train Batch ===")
for seq_batch, label_batch in train_loader:print("Sequences:", seq_batch)print("Labels: ", label_batch)breakprint("\n=== Test Batch ===")
for seq_batch, label_batch in test_loader:print("Sequences:", seq_batch)print("Labels: ", label_batch)break
