单身Python发电机？或者,腌制Python发电机？

2019年7月29日 145次阅读

我使用以下代码,使用嵌套生成器,迭代文本文档并使用get_train_minibatch()返回训练示例.我想坚持(挑选)发电机,所以我可以回到文本文件中的同一个地方.但是,你不能腌制发电机.

>是否有一个简单的解决方法,以便我可以保存我的位置并从我停止的地方开始？也许我可以让get_train_example()成为一个单身人士,所以我没有几个生成器.然后,我可以在这个模块中创建一个全局变量来跟踪get_train_example()的走向.
>你有一个更好(更清洁)的建议,让我坚持这个发电机？

[编辑：另外两个想法：

>我可以向生成器添加成员变量/方法,所以我可以调用generator.tell()并找到文件位置吗？因为那时,下次我创建生成器时,我可以要求它寻找那个位置.这个想法听起来最简单.
>我可以创建一个类并将文件位置设置为成员变量,然后在类中创建生成器并在每次生成时更新文件位置成员变量吗？因为那时我可以知道它进入文件的距离.

]

这是代码：

def get_train_example():
    for l in open(HYPERPARAMETERS["TRAIN_SENTENCES"]):
        prevwords = []
        for w in string.split(l):
            w = string.strip(w)
            id = None
            prevwords.append(wordmap.id(w))
            if len(prevwords) >= HYPERPARAMETERS["WINDOW_SIZE"]:
                yield prevwords[-HYPERPARAMETERS["WINDOW_SIZE"]:]

def get_train_minibatch():
    minibatch = []
    for e in get_train_example():
        minibatch.append(e)
        if len(minibatch) >= HYPERPARAMETERS["MINIBATCH SIZE"]:
            assert len(minibatch) == HYPERPARAMETERS["MINIBATCH SIZE"]
            yield minibatch
            minibatch = []

最佳答案 以下代码应该或多或少地执行您想要的操作.第一个类定义了一些像文件一样但可以被pickle的东西. (当你取消它时,它重新打开文件,并寻找到它腌制时的位置).第二个类是生成单词窗口的迭代器.

class PickleableFile(object):
    def __init__(self, filename, mode='rb'):
        self.filename = filename
        self.mode = mode
        self.file = open(filename, mode)
    def __getstate__(self):
        state = dict(filename=self.filename, mode=self.mode,
                     closed=self.file.closed)
        if not self.file.closed:
            state['filepos'] = self.file.tell()
        return state
    def __setstate__(self, state):
        self.filename = state['filename']
        self.mode = state['mode']
        self.file = open(self.filename, self.mode)
        if state['closed']: self.file.close()
        else: self.file.seek(state['filepos'])
    def __getattr__(self, attr):
        return getattr(self.file, attr)

class WordWindowReader:
    def __init__(self, filenames, window_size):
        self.filenames = filenames
        self.window_size = window_size
        self.filenum = 0
        self.stream = None
        self.filepos = 0
        self.prevwords = []
        self.current_line = []

    def __iter__(self):
        return self

    def next(self):
        # Read through files until we have a non-empty current line.
        while not self.current_line:
            if self.stream is None:
                if self.filenum >= len(self.filenames):
                    raise StopIteration
                else:
                    self.stream = PickleableFile(self.filenames[self.filenum])
                    self.stream.seek(self.filepos)
                    self.prevwords = []
            line = self.stream.readline()
            self.filepos = self.stream.tell()
            if line == '':
                # End of file.
                self.stream = None
                self.filenum += 1
                self.filepos = 0
            else:
                # Reverse line so we can pop off words.
                self.current_line = line.split()[::-1]

        # Get the first word of the current line, and add it to
        # prevwords.  Truncate prevwords when necessary.
        word = self.current_line.pop()
        self.prevwords.append(word)
        if len(self.prevwords) > self.window_size:
            self.prevwords = self.prevwords[-self.window_size:]

        # If we have enough words, then return a word window;
        # otherwise, go on to the next word.
        if len(self.prevwords) == self.window_size:
            return self.prevwords
        else:
            return self.next()
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