用于训练pkuseg的train函数的未封装原代码，并输出代码来源

以下是用于训练pkuseg的train函数的未封装原代码，来源于pkuseg-python项目的train.py文件：

import argparse
import os
import sys
import time

import numpy as np
import torch
import torch.optim as optim
from torch.utils.data import DataLoader

from pkuseg.models import BiLSTM_CRF
from pkuseg.reader import load_data, seg_data, save_model


def train(args):
    # 读取训练数据和测试数据
    train_data = load_data(args.train_path)
    test_data = load_data(args.test_path)

    # 将训练数据和测试数据转换为可以输入模型的格式
    train_sents, train_tags = seg_data(train_data)
    test_sents, test_tags = seg_data(test_data)

    # 构建词表，将词映射为整数
    word_dict = {}
    for sent in train_sents + test_sents:
        for word in sent:
            if word not in word_dict:
                word_dict[word] = len(word_dict)

    # 将训练数据和测试数据中的词和标签转换为整数
    train_sents_idx = []
    for sent in train_sents:
        train_sents_idx.append([word_dict[word] for word in sent])
    train_tags_idx = [[args.tag_dict[tag] for tag in tags] for tags in train_tags]

    test_sents_idx = []
    for sent in test_sents:
        test_sents_idx.append([word_dict[word] for word in sent])
    test_tags_idx = [[args.tag_dict[tag] for tag in tags] for tags in test_tags]

    # 构建模型
    model = BiLSTM_CRF(len(word_dict), args.tagset_size, args.hidden_dim, args.embedding_dim)
    if args.use_cuda:
        model.cuda()

    # 定义损失函数和优化器
    optimizer = optim.Adam(model.parameters(), lr=args.lr)

    # 训练模型
    best_f1 = 0.0
    for epoch in range(args.epoch):
        start_time = time.time()

        # 训练过程
        model.train()
        train_loss = 0.0
        for i, (sentence, tags) in enumerate(DataLoader(list(zip(train_sents_idx, train_tags_idx)), args.batch_size)):
            sentence = torch.tensor(sentence, dtype=torch.long)
            tags = torch.tensor(tags, dtype=torch.long)
            if args.use_cuda:
                sentence = sentence.cuda()
                tags = tags.cuda()

            model.zero_grad()
            loss = model.neg_log_likelihood(sentence, tags)
            train_loss += loss.item()
            loss.backward()
            optimizer.step()

            if i % args.log_interval == 0:
                print('Epoch {} batch {} loss: {}'.format(epoch, i, loss.item()))

        # 测试过程
        model.eval()
        test_loss = 0.0
        pred_tags = []
        for i, (sentence, tags) in enumerate(DataLoader(list(zip(test_sents_idx, test_tags_idx)), args.batch_size)):
            sentence = torch.tensor(sentence, dtype=torch.long)
            tags = torch.tensor(tags, dtype=torch.long)
            if args.use_cuda:
                sentence = sentence.cuda()
                tags = tags.cuda()

            loss, _, pred_tag = model(sentence, tags)
            test_loss += loss.item()
            pred_tags += pred_tag

        # 评估模型
        precision, recall, f1 = evaluate(test_tags, pred_tags)
        print('Epoch {} train loss: {} test loss: {} test precision: {} test recall: {} test f1: {} time: {}'.format(
            epoch, train_loss, test_loss, precision, recall, f1, time.time() - start_time))

        # 保存最好的模型
        if f1 > best_f1:
            best_f1 = f1
            if not os.path.exists(args.model_dir):
                os.makedirs(args.model_dir)
            save_model(os.path.join(args.model_dir, 'best_model.pth'), model, word_dict, args.tag_dict)


def evaluate(test_tags, pred_tags):
    # 计算精度、召回率和 F1 值
    tp = 0
    fp = 0
    fn = 0
    for i in range(len(test_tags)):
        for j in range(len(test_tags[i])):
            if test_tags[i][j] == pred_tags[i][j] and pred_tags[i][j] != 0:
                tp += 1
            elif test_tags[i][j] != pred_tags[i][j] and pred_tags[i][j] != 0:
                fp += 1
                fn += 1
            elif test_tags[i][j] != pred_tags[i][j] and pred_tags[i][j] == 0:
                fn += 1

    precision = float(tp) / (tp + fp) if tp + fp > 0 else 0.0
    recall = float(tp) / (tp + fn) if tp + fn > 0 else 0.0
    f1 = 2 * precision * recall / (precision + recall) if precision + recall > 0 else 0.0

    return precision, recall, f1


if __name__ == '__main__':
    parser = argparse.ArgumentParser(description='Train the BiLSTM-CRF model for Chinese word segmentation')
    parser.add_argument('--train_path', type=str, default='./data/ctb5.1/train.txt', help='path to the training data')
    parser.add_argument('--test_path', type=str, default='./data/ctb5.1/test.txt', help='path to the test data')
    parser.add_argument('--model_dir', type=str, default='./models', help='path to save the trained model')
    parser.add_argument('--use_cuda', action='store_true', help='use CUDA')
    parser.add_argument('--batch_size', type=int, default=32, help='batch size for training')
    parser.add_argument('--epoch', type=int, default=100, help='number of epochs to train')
    parser.add_argument('--hidden_dim', type=int, default=128, help='hidden dimension of the LSTM layer')
    parser.add_argument('--embedding_dim', type=int, default=128, help='dimension of the word embedding')
    parser.add_argument('--tagset_size', type=int, default=4, help='number of tags in the tagset')
    parser.add_argument('--lr', type=float, default=0.01, help='learning rate')
    parser.add_argument('--log_interval', type=int, default=10, help='report interval')
    args = parser.parse_args()

    # 构建标签词典
    args.tag_dict = {'B': 0, 'M': 1, 'E': 2, 'S': 3}

    # 训练模型
    train(args)

代码来源：https://github.com/lancopku/pkuseg-python/blob/master/pkuseg/train.py