1. 机器翻译与数据集

import os
import torch
from d2l import torch as d2l#@save
d2l.DATA_HUB['fra-eng'] = (d2l.DATA_URL + 'fra-eng.zip','94646ad1522d915e7b0f9296181140edcf86a4f5')#@save
def read_data_nmt():"""载入“英语－法语”数据集"""data_dir = d2l.download_extract('fra-eng')with open(os.path.join(data_dir, 'fra.txt'), 'r',encoding='utf-8') as f:return f.read()raw_text = read_data_nmt()
print(raw_text[:75])#@save
# 标点符号也要翻译
def preprocess_nmt(text):"""预处理“英语－法语”数据集"""def no_space(char, prev_char):return char in set(',.!?') and prev_char != ' '# 使用空格替换不间断空格# 使用小写字母替换大写字母text = text.replace('\u202f', ' ').replace('\xa0', ' ').lower()# 在单词和标点符号之间插入空格out = [' ' + char if i > 0 and no_space(char, text[i - 1]) else charfor i, char in enumerate(text)]return ''.join(out)text = preprocess_nmt(raw_text)
print(text[:80])#@save
def tokenize_nmt(text, num_examples=None):"""词元化“英语－法语”数据数据集"""source, target = [], []for i, line in enumerate(text.split('\n')):if num_examples and i > num_examples:breakparts = line.split('\t')if len(parts) == 2:source.append(parts[0].split(' '))target.append(parts[1].split(' '))return source, target
#  英语   法语
source, target = tokenize_nmt(text)
source[:6], target[:6]#@save
def show_list_len_pair_hist(legend, xlabel, ylabel, xlist, ylist):"""绘制列表长度对的直方图"""d2l.set_figsize()_, _, patches = d2l.plt.hist([[len(l) for l in xlist], [len(l) for l in ylist]])d2l.plt.xlabel(xlabel)d2l.plt.ylabel(ylabel)for patch in patches[1].patches:patch.set_hatch('/')d2l.plt.legend(legend)show_list_len_pair_hist(['source', 'target'], '# tokens per sequence','count', source, target);# <pad> 填充  <bos> 句子开始  <eos> 句子结束
# 词小于等于2 就不要了。
src_vocab = d2l.Vocab(source, min_freq=2,reserved_tokens=['<pad>', '<bos>', '<eos>'])
len(src_vocab)# 怎么让句子变成一样的长度  填充或者删除。
#@save
def truncate_pad(line, num_steps, padding_token):"""截断或填充文本序列"""if len(line) > num_steps:return line[:num_steps]  # 截断return line + [padding_token] * (num_steps - len(line))  # 填充truncate_pad(src_vocab[source[0]], 10, src_vocab['<pad>'])#@save
# valid_len 告诉句子实际长度是多少【记录原始数据多长】 不管填充的内容，计算时不要学pad
def build_array_nmt(lines, vocab, num_steps):"""将机器翻译的文本序列转换成小批量"""lines = [vocab[l] for l in lines]lines = [l + [vocab['<eos>']] for l in lines]array = torch.tensor([truncate_pad(l, num_steps, vocab['<pad>']) for l in lines])valid_len = (array != vocab['<pad>']).type(torch.int32).sum(1)return array, valid_len#@save
def load_data_nmt(batch_size, num_steps, num_examples=600):"""返回翻译数据集的迭代器和词表"""text = preprocess_nmt(read_data_nmt())source, target = tokenize_nmt(text, num_examples)src_vocab = d2l.Vocab(source, min_freq=2,reserved_tokens=['<pad>', '<bos>', '<eos>'])tgt_vocab = d2l.Vocab(target, min_freq=2,reserved_tokens=['<pad>', '<bos>', '<eos>'])src_array, src_valid_len = build_array_nmt(source, src_vocab, num_steps)tgt_array, tgt_valid_len = build_array_nmt(target, tgt_vocab, num_steps)data_arrays = (src_array, src_valid_len, tgt_array, tgt_valid_len)data_iter = d2l.load_array(data_arrays, batch_size)return data_iter, src_vocab, tgt_vocabtrain_iter, src_vocab, tgt_vocab = load_data_nmt(batch_size=2, num_steps=8)
for X, X_valid_len, Y, Y_valid_len in train_iter:print('X:', X.type(torch.int32))print('X的有效长度:', X_valid_len)print('Y:', Y.type(torch.int32))print('Y的有效长度:', Y_valid_len)break