以下是一份关于 transformers
库的全面讲解,包含基础知识、高级用法、案例代码及学习路径。内容经过组织,适合不同阶段的学习者。
Tokenizer
:文本分词与编码Model
:神经网络模型架构Pipeline
:快速推理的封装接口pip install transformers torch datasets
from transformers import pipeline
# 使用情感分析流水线
classifier = pipeline("sentiment-analysis")
result = classifier("I love programming with Transformers!")
print(result) # [{'label': 'POSITIVE', 'score': 0.9998}]
from transformers import AutoTokenizer
tokenizer = AutoTokenizer.from_pretrained("bert-base-uncased")
text = "Hello, world!"
encoded = tokenizer(text,
padding=True,
truncation=True,
return_tensors="pt") # 返回PyTorch张量
print(encoded)
# {'input_ids': tensor([[101, 7592, 1010, 2088, 999, 102]]),
# 'attention_mask': tensor([[1, 1, 1, 1, 1, 1]])}
from transformers import AutoModel
model = AutoModel.from_pretrained("bert-base-uncased")
outputs = model(**encoded) # 前向传播
last_hidden_states = outputs.last_hidden_state
from transformers import BertForSequenceClassification, Trainer, TrainingArguments
from datasets import load_dataset
# 加载数据集
dataset = load_dataset("imdb")
tokenized_datasets = dataset.map(
lambda x: tokenizer(x["text"], padding=True, truncation=True),
batched=True
)
# 定义模型
model = BertForSequenceClassification.from_pretrained("bert-base-uncased", num_labels=2)
# 训练参数配置
training_args = TrainingArguments(
output_dir="./results",
num_train_epochs=3,
per_device_train_batch_size=8,
evaluation_strategy="epoch"
)
# 训练器配置
trainer = Trainer(
model=model,
args=training_args,
train_dataset=tokenized_datasets["train"],
eval_dataset=tokenized_datasets["test"]
)
# 开始训练
trainer.train()
model.save_pretrained("./my_model")
tokenizer.save_pretrained("./my_model")
# 加载自定义模型
new_model = AutoModel.from_pretrained("./my_model")
from transformers import BertModel, BertTokenizer
import torch
model = BertModel.from_pretrained("bert-base-uncased", output_attentions=True)
inputs = tokenizer("The cat sat on the mat", return_tensors="pt")
outputs = model(**inputs)
# 提取第0层的注意力权重
attention = outputs.attentions[0][0]
print(attention.shape) # [num_heads, seq_len, seq_len]
from transformers import TrainingArguments
training_args = TrainingArguments(
fp16=True, # 启用混合精度
...
)
from transformers import pipeline
# 加载NER流水线
ner_pipeline = pipeline("ner", model="dslim/bert-base-NER")
text = "Apple was founded by Steve Jobs in Cupertino."
results = ner_pipeline(text)
# 结果可视化
for entity in results:
print(f"{entity['word']} -> {entity['entity']} (confidence: {entity['score']:.2f})")
pipeline
和基础模型使用在训练过程中动态调整学习率,防止梯度爆炸:
from transformers import TrainingArguments
training_args = TrainingArguments(
output_dir="./results",
learning_rate=2e-5,
weight_decay=0.01,
warmup_steps=500, # 学习率预热步数
gradient_accumulation_steps=2, # 梯度累积(节省显存)
gradient_clipping=1.0, # 梯度裁剪阈值
...
)
import torch
from transformers import BertForSequenceClassification
class CustomModel(BertForSequenceClassification):
def __init__(self, config):
super().__init__(config)
def forward(self, input_ids, attention_mask, labels=None):
outputs = super().forward(input_ids, attention_mask)
logits = outputs.logits
if labels is not None:
loss_fct = torch.nn.CrossEntropyLoss(weight=torch.tensor([1.0, 2.0])) # 类别权重
loss = loss_fct(logits.view(-1, 2), labels.view(-1))
return {"loss": loss, "logits": logits}
return outputs
from transformers import GPT2LMHeadModel, GPT2Tokenizer
tokenizer = GPT2Tokenizer.from_pretrained("gpt2")
model = GPT2LMHeadModel.from_pretrained("gpt2")
prompt = "In a world where AI dominates,"
input_ids = tokenizer.encode(prompt, return_tensors="pt")
# 生成文本(配置生成参数)
output = model.generate(
input_ids,
max_length=100,
temperature=0.7, # 控制随机性(低值更确定)
top_k=50, # 限制候选词数量
num_return_sequences=3 # 生成3个不同结果
)
for seq in output:
print(tokenizer.decode(seq, skip_special_tokens=True))
from transformers import pipeline
qa_pipeline = pipeline("question-answering", model="deepset/roberta-base-squad2")
context = """
Hugging Face is a company based in New York City.
Its Transformers library is widely used in NLP.
"""
question = "Where is Hugging Face located?"
result = qa_pipeline(question=question, context=context)
print(f"Answer: {result['answer']} (score: {result['score']:.2f})")
# Answer: New York City (score: 0.92)
from transformers import BertModel, AutoTokenizer
import torch
model = BertModel.from_pretrained("bert-base-uncased")
quantized_model = torch.quantization.quantize_dynamic(
model,
{torch.nn.Linear}, # 量化所有线性层
dtype=torch.qint8
)
# 量化后推理速度提升2-4倍,模型体积减少约75%
from transformers import BertTokenizer, BertForSequenceClassification
from torch.onnx import export
model = BertForSequenceClassification.from_pretrained("bert-base-uncased")
tokenizer = BertTokenizer.from_pretrained("bert-base-uncased")
# 示例输入
dummy_input = tokenizer("This is a test", return_tensors="pt")
# 导出为ONNX
export(
model,
(dummy_input["input_ids"], dummy_input["attention_mask"]),
"model.onnx",
opset_version=13,
input_names=["input_ids", "attention_mask"],
output_names=["logits"],
dynamic_axes={"input_ids": {0: "batch"}, "attention_mask": {0: "batch"}}
)
import torch
# 在训练循环中插入显存监控
print(f"Allocated: {torch.cuda.memory_allocated() / 1e9:.2f} GB")
print(f"Cached: {torch.cuda.memory_reserved() / 1e9:.2f} GB")
from torch.profiler import profile, record_function, ProfilerActivity
with profile(activities=[ProfilerActivity.CUDA], record_shapes=True) as prof:
outputs = model(**inputs)
print(prof.key_averages().table(sort_by="cuda_time_total", row_limit=10))
from transformers import MBartForConditionalGeneration, MBart50TokenizerFast
model = MBartForConditionalGeneration.from_pretrained("facebook/mbart-large-50-many-to-many-mmt")
tokenizer = MBart50TokenizerFast.from_pretrained("facebook/mbart-large-50-many-to-many-mmt")
# 中文转英文
tokenizer.src_lang = "zh_CN"
text = "欢迎使用Transformers库"
encoded = tokenizer(text, return_tensors="pt")
generated_tokens = model.generate(**encoded, forced_bos_token_id=tokenizer.lang_code_to_id["en_XX"])
print(tokenizer.batch_decode(generated_tokens, skip_special_tokens=True))
# ['Welcome to the Transformers library']
from PIL import Image
from transformers import CLIPProcessor, CLIPModel
model = CLIPModel.from_pretrained("openai/clip-vit-base-patch32")
processor = CLIPProcessor.from_pretrained("openai/clip-vit-base-patch32")
image = Image.open("cat.jpg")
text = ["a photo of a cat", "a photo of a dog"]
inputs = processor(text=text, images=image, return_tensors="pt", padding=True)
outputs = model(**inputs)
# 计算图文相似度
logits_per_image = outputs.logits_per_image
probs = logits_per_image.softmax(dim=1) # 概率分布
import torch.nn as nn
class TransformerBlock(nn.Module):
def __init__(self, d_model=512, nhead=8):
super().__init__()
self.attention = nn.MultiheadAttention(d_model, nhead)
self.linear = nn.Linear(d_model, d_model)
self.norm = nn.LayerNorm(d_model)
def forward(self, x):
attn_output, _ = self.attention(x, x, x)
x = x + attn_output
x = self.norm(x)
x = x + self.linear(x)
return x
batch_size
gradient_accumulation_steps
)fp16=True
)torch.cuda.empty_cache()
from transformers import BertTokenizer
tokenizer = BertTokenizer.from_pretrained("bert-base-chinese")
# 手动添加特殊词汇
tokenizer.add_tokens(["【特殊词】"])
# 调整模型嵌入层
model.resize_token_embeddings(len(tokenizer))
以下继续扩展关于 transformers
库的深度应用内容,涵盖更多实际场景、前沿技术及工业级实践方案。
from transformers import LlamaForCausalLM, LlamaTokenizer, TrainingArguments
# 加载模型和分词器(需申请权限)
model = LlamaForCausalLM.from_pretrained("decapoda-research/llama-7b-hf")
tokenizer = LlamaTokenizer.from_pretrained("decapoda-research/llama-7b-hf")
# 低秩适配(LoRA)微调
from peft import get_peft_model, LoraConfig
lora_config = LoraConfig(
r=8, # 低秩维度
lora_alpha=32,
target_modules=["q_proj", "v_proj"], # 仅微调部分模块
lora_dropout=0.05,
bias="none"
)
model = get_peft_model(model, lora_config)
model.print_trainable_parameters() # 显示可训练参数占比(通常 <1%)
# 继续配置训练参数...
# 使用 TRL 库进行 RLHF 训练
from trl import PPOTrainer, AutoModelForCausalLMWithValueHead
model = AutoModelForCausalLMWithValueHead.from_pretrained("gpt2")
ppo_trainer = PPOTrainer(
model=model,
config=training_args,
dataset=dataset,
tokenizer=tokenizer
)
# 定义奖励模型
for epoch in range(3):
for batch in ppo_trainer.dataloader:
# 生成响应
response_tensors = model.generate(batch["input_ids"])
# 计算奖励(需自定义奖励函数)
rewards = calculate_rewards(response_tensors, batch)
# PPO 优化步骤
ppo_trainer.step(
response_tensors,
rewards,
batch["attention_mask"]
)
from transformers import TrainingArguments
# 配置分布式训练
training_args = TrainingArguments(
per_device_train_batch_size=4,
gradient_accumulation_steps=8,
fp16=True,
tpu_num_cores=8, # 使用TPU时指定核心数
dataloader_num_workers=4,
deepspeed="./configs/deepspeed_config.json" # 使用DeepSpeed优化
)
# DeepSpeed 配置文件示例(ds_config.json):
{
"fp16": {
"enabled": true
},
"optimizer": {
"type": "AdamW",
"params": {
"lr": 3e-5
}
},
"zero_optimization": {
"stage": 3 # 启用ZeRO-3优化
}
}
from fastapi import FastAPI
from pydantic import BaseModel
from transformers import pipeline
app = FastAPI()
generator = pipeline("text-generation", model="gpt2")
class Request(BaseModel):
text: str
max_length: int = 100
@app.post("/generate")
async def generate_text(request: Request):
result = generator(request.text, max_length=request.max_length)
return {"generated_text": result[0]["generated_text"]}
# 启动服务:uvicorn main:app --port 8000
from transformers import AutoTokenizer, AutoModelForQuestionAnswering
tokenizer = AutoTokenizer.from_pretrained("bert-large-uncased-whole-word-masking-finetuned-squad")
model = AutoModelForQuestionAnswering.from_pretrained("bert-large-uncased-whole-word-masking-finetuned-squad")
def process_long_text(context, question, max_length=384, stride=128):
# 分块处理长文本
inputs = tokenizer(
question,
context,
max_length=max_length,
truncation="only_second",
stride=stride,
return_overflowing_tokens=True,
return_offsets_mapping=True
)
# 对各块推理并合并结果
best_score = 0
best_answer = ""
for i in range(len(inputs["input_ids"])):
outputs = model(**{k: torch.tensor([v[i]]) for k, v in inputs.items()})
answer_start = torch.argmax(outputs.start_logits)
answer_end = torch.argmax(outputs.end_logits) + 1
score = (outputs.start_logits[answer_start] + outputs.end_logits[answer_end-1]).item()
if score > best_score:
best_score = score
best_answer = tokenizer.decode(inputs["input_ids"][i][answer_start:answer_end])
return best_answer
# 使用 XLM-RoBERTa 进行跨语言迁移
from transformers import XLMRobertaTokenizer, XLMRobertaForSequenceClassification
tokenizer = XLMRobertaTokenizer.from_pretrained("xlm-roberta-base")
model = XLMRobertaForSequenceClassification.from_pretrained("xlm-roberta-base")
# 通过少量样本微调(代码与BERT训练类似)
from captum.attr import LayerIntegratedGradients
from transformers import BertForSequenceClassification
model = BertForSequenceClassification.from_pretrained("bert-base-uncased")
def forward_func(input_ids, attention_mask):
return model(input_ids, attention_mask).logits
lig = LayerIntegratedGradients(forward_func, model.bert.embeddings)
# 计算输入词重要性
attributions, delta = lig.attribute(
inputs=input_ids,
baselines=tokenizer.pad_token_id * torch.ones_like(input_ids),
additional_forward_args=attention_mask,
return_convergence_delta=True
)
# 可视化结果
import matplotlib.pyplot as plt
plt.bar(range(len(attributions[0])), attributions[0].detach().numpy())
plt.xticks(ticks=range(len(tokens)), labels=tokens, rotation=90)
plt.show()
import spacy
from spacy_transformers import TransformersLanguage, TransformersWordPiecer
# 创建spacy管道
nlp = TransformersLanguage(trf_name="bert-base-uncased")
# 自定义组件
@spacy.registry.architectures("CustomClassifier.v1")
def create_classifier(transformer, tok2vec, n_classes):
return TransformersTextCategorizer(transformer, tok2vec, n_classes)
# 在spacy中直接使用Transformer模型
doc = nlp("This is a text to analyze.")
print(doc._.trf_last_hidden_state.shape) # [seq_len, hidden_dim]
import gradio as gr
from transformers import pipeline
ner_pipeline = pipeline("ner")
def extract_entities(text):
results = ner_pipeline(text)
return {"text": text, "entities": [
{"entity": res["entity"], "start": res["start"], "end": res["end"]}
for res in results
]}
gr.Interface(
fn=extract_entities,
inputs=gr.Textbox(lines=5),
outputs=gr.HighlightedText()
).launch()
跟踪最新进展:
实战项目进阶:
系统优化方向:
以下继续扩展关于 transformers
库的终极实践指南,涵盖生产级优化、前沿模型架构、领域专用方案及伦理考量。
# 使用 nn_pruning 进行结构化剪枝
from transformers import BertForSequenceClassification
from nn_pruning import ModelPruning
model = BertForSequenceClassification.from_pretrained("bert-base-uncased")
pruner = ModelPruning(
model,
target_sparsity=0.5, # 剪枝50%的注意力头
pattern="block_sparse" # 结构化剪枝模式
)
# 执行剪枝并微调
pruned_model = pruner.prune()
pruned_model.save_pretrained("./pruned_bert")
# 知识蒸馏(教师→学生模型)
from transformers import DistilBertForSequenceClassification, DistilBertTokenizer
teacher = BertForSequenceClassification.from_pretrained("bert-base-uncased")
student = DistilBertForSequenceClassification.from_pretrained("distilbert-base-uncased")
# 使用蒸馏训练器
from transformers import DistillationTrainingArguments, DistillationTrainer
training_args = DistillationTrainingArguments(
output_dir="./distilled",
temperature=2.0, # 软化概率分布
alpha_ce=0.5, # 交叉熵损失权重
alpha_mse=0.5 # 隐藏层MSE损失权重
)
trainer = DistillationTrainer(
teacher=teacher,
student=student,
args=training_args,
train_dataset=tokenized_datasets["train"],
tokenizer=tokenizer
)
trainer.train()
# 转换模型为TensorRT引擎
trtexec --onnx=model.onnx --saveEngine=model.trt --fp16
# Python 调用TensorRT引擎
import tensorrt as trt
import pycuda.driver as cuda
runtime = trt.Runtime(trt.Logger(trt.Logger.WARNING))
with open("model.trt", "rb") as f:
engine = runtime.deserialize_cuda_engine(f.read())
context = engine.create_execution_context()
# 绑定输入输出缓冲区进行推理
from transformers import AutoTokenizer, AutoModelForTokenClassification
tokenizer = AutoTokenizer.from_pretrained("dmis-lab/biobert-v1.1")
model = AutoModelForTokenClassification.from_pretrained("dmis-lab/biobert-v1.1")
text = "The patient exhibited EGFR mutations and responded to osimertinib."
inputs = tokenizer(text, return_tensors="pt")
outputs = model(**inputs).logits
# 提取基因实体
predictions = torch.argmax(outputs, dim=2)
print([tokenizer.decode([token]) for token in inputs.input_ids[0]])
print(predictions.tolist()) # BIO标注结果
# 合同条款分类
from transformers import BertTokenizer, BertForSequenceClassification
tokenizer = BertTokenizer.from_pretrained("nlpaueb/legal-bert-base-uncased")
model = BertForSequenceClassification.from_pretrained("nlpaueb/legal-bert-base-uncased")
clause = "The Parties hereby agree to arbitrate all disputes in accordance with ICC rules."
inputs = tokenizer(clause, return_tensors="pt", truncation=True, padding=True)
outputs = model(**inputs)
predicted_class = torch.argmax(outputs.logits).item() # 0: 仲裁条款, 1: 保密条款等
from transformers import BertForSequenceClassification
import coremltools as ct
model = BertForSequenceClassification.from_pretrained("bert-base-uncased")
tokenizer = BertTokenizer.from_pretrained("bert-base-uncased")
# 转换模型
traced_model = torch.jit.trace(model, (input_ids, attention_mask))
mlmodel = ct.convert(
traced_model,
inputs=[
ct.TensorType(name="input_ids", shape=input_ids.shape),
ct.TensorType(name="attention_mask", shape=attention_mask.shape)
]
)
mlmodel.save("BertSenti.mlmodel")
from transformers import TFBertForSequenceClassification
import tensorflow as tf
model = TFBertForSequenceClassification.from_pretrained("bert-base-uncased")
# 转换为TFLite
converter = tf.lite.TFLiteConverter.from_keras_model(model)
converter.optimizations = [tf.lite.Optimize.DEFAULT] # 动态范围量化
tflite_model = converter.convert()
with open("model_quant.tflite", "wb") as f:
f.write(tflite_model)
from transformers import pipeline
from fairness_metrics import demographic_parity
# 检测模型偏见
classifier = pipeline("text-classification", model="bert-base-uncased")
protected_groups = {
"gender": ["she", "he"],
"race": ["African", "European"]
}
bias_scores = {}
for category, terms in protected_groups.items():
texts = [f"{term} is qualified for this position" for term in terms]
results = classifier(texts)
bias_scores[category] = demographic_parity(results)
from textattack import AttackRecipe
from textattack.models.wrappers import HuggingFaceModelWrapper
model_wrapper = HuggingFaceModelWrapper(model, tokenizer)
attack = AttackRecipe.build("bae") # BAE攻击方法
# 生成对抗样本
attack_args = textattack.AttackArgs(num_examples=5)
attacker = textattack.Attacker(attack, model_wrapper, attack_args)
attack_results = attacker.attack_dataset(dataset)
from transformers import LongformerModel
model = LongformerModel.from_pretrained("allenai/longformer-base-4096")
inputs = tokenizer("This is a very long document..."*1000, return_tensors="pt")
outputs = model(**inputs) # 支持最长4096 tokens
# 使用Switch Transformers
from transformers import SwitchTransformersForConditionalGeneration
model = SwitchTransformersForConditionalGeneration.from_pretrained("google/switch-base-8")
outputs = model.generate(
input_ids,
expert_choice_mask=True, # 追踪专家路由
)
print(outputs.expert_choices) # 显示每个token使用的专家
"""
端到端文本分类系统架构:
1. 数据采集 → 2. 清洗 → 3. 标注 → 4. 模型训练 → 5. 评估 → 6. 部署 → 7. 监控
"""
# 步骤4的增强训练流程
from transformers import TrainerCallback
class CustomCallback(TrainerCallback):
def on_log(self, args, state, control, logs=None, **kwargs):
# 实时记录指标到Prometheus
prometheus_logger.log_metrics(logs)
# 步骤7的漂移检测
from alibi_detect.cd import MMDDrift
detector = MMDDrift(
X_train,
backend="tensorflow",
p_val=0.05
)
drift_preds = detector.predict(X_prod)
技术跟踪:
技能扩展:
跨界融合:
伦理实践: