keras实战教程一(NER)

NLP四大任务：序列标注（分词，NER），文本分类（情感分析），句子关系判断（语意相似判断），句子生成（机器翻译）

什么是序列标注

以命名实体识别为例，识别一句话中的人名地名组织时间等都属于序列标注问题。NER 的任务就是要将这些包含信息的或者专业领域的实体给识别出来

示例

句子：[我在上海工作]
tag : [O,O,B_LOC,I_LOC,O,O]

数据

数据地址

训练数据样

 

 模型

BiLSTM+CRF

LSTM 强大的拟合能力可以很好的完成这个序列标注问题。
CRF能记住实体序列的规则。它的作用是纠正LSTM的一些低级错误。

论文：CNN+BiLSTM+CRF论文

模型图

 代码

数据处理

import pickle
import numpy as np
from keras.preprocessing.sequence import pad_sequences
from keras import Sequential
from keras_contrib.layers import CRF
import pickle
from keras.layers import Embedding ,Bidirectional,LSTM


class Data_set:
    def __init__(self,data_path,labels):
        with open(data_path,"rb") as f:
            self.data = f.read().decode("utf-8")
        self.process_data = self.process_data()
        self.labels = labels
    def process_data(self):
        train_data =self.data.split("

")
        train_data = [token.split("
") for token in train_data]
        train_data = [[j.split() for j in i ] for i in train_data]
        train_data.pop()
        return train_data
    
    def save_vocab(self,save_path):
        all_char = [ char[0] for sen in self.process_data for char in sen]
        chars = set(all_char)
        word2id = {char:id_+1 for id_,char in enumerate(chars)}
        word2id["unk"] = 0
        with open (save_path,"wb") as f:
            pickle.dump(word2id,f)
        return word2id    
    
    def generate_data(self,vocab,maxlen):
        char_data_sen = [[token[0] for token in i ] for i in self.process_data]
        label_sen = [[token[1] for token in i ] for i in self.process_data]
        sen2id = [[ vocab.get(char,0) for char in sen] for sen in char_data_sen]
        label2id = {label:id_ for id_,label in enumerate(self.labels)}
        lab_sen2id = [[label2id.get(lab,0) for lab in sen] for sen in label_sen]
        sen_pad = pad_sequences(sen2id,maxlen)
        lab_pad = pad_sequences(lab_sen2id,maxlen,value=-1)
        lab_pad = np.expand_dims(lab_pad, 2)
        return sen_pad ,lab_pad

环境：keras==2.2.4 tf==1.12.0   安装keras-contrib ：pip install git+https://www.github.com/keras-team/keras-contrib.git

data = Data_set("train_data.data",['O', 'B-PER', 'I-PER', 'B-LOC', 'I-LOC', "B-ORG", "I-ORG"])
vocab = data.save_vocab("vocab.pk")
sentence,sen_tags= data.generate_data(vocab,200)

构建模型

class Ner:
    def __init__(self,vocab,labels_category,Embedding_dim=200):
        self.Embedding_dim = Embedding_dim
        self.vocab = vocab
        self.labels_category = labels_category
        self.model = self.build_model()
        
    def build_model(self):
        model = Sequential()
        model.add(Embedding(len(self.vocab),self.Embedding_dim,mask_zero=True))  # Random embedding
        model.add(Bidirectional(LSTM(100, return_sequences=True)))
        crf = CRF(len(self.labels_category), sparse_target=True)
        model.add(crf)
        model.summary()
        model.compile('adam', loss=crf.loss_function, metrics=[crf.accuracy])
        return model
    
    def train(self,data,label,EPOCHS):
        self.model.fit(data,label,batch_size=16,epochs=EPOCHS)
        self.model.save('crf.h5')
        
    def predict(self,model_path,data,maxlen):
        model =self.model
        char2id = [self.vocab.get(i) for i in data]
        pad_num = maxlen - len(char2id)
        input_data = pad_sequences([char2id],maxlen)
        model.load_weights(model_path)
        result = model.predict(input_data)[0][-len(data):]
        result_label = [np.argmax(i) for i in result]
        return result_label

tags = ['O', 'B-PER', 'I-PER', 'B-LOC', 'I-LOC', "B-ORG", "I-ORG"]
ner = Ner(vocab,tags)

训练预测

ner.train(sentence,sen_tags,1)

sen_test = "北京故宫，清华大学图书馆"
res = ner.predict("./crf.h5",sen_test,200)
label =  ['O', 'B-PER', 'I-PER', 'B-LOC', 'I-LOC', "B-ORG", "I-ORG"]
res2label =[label[i] for i in res]
per, loc, org = '', '', ''
for s, t in zip(a, res2label):
    if t in ('B-PER', 'I-PER'):
        per += ' ' + s if (t == 'B-PER') else s
    if t in ('B-ORG', 'I-ORG'):
        org += ' ' + s if (t == 'B-ORG') else s
    if t in ('B-LOC', 'I-LOC'):
        loc += ' ' + s if (t == 'B-LOC') else s
print("人名:",per)    
print("地名:",loc)
print("组织名:",org)

 参考：https://www.jianshu.com/p/6668b965583e