Question

我编写了一个类，它从文件中读取数据，并使其可用于以更大程序的其他部分的可用形式进行操作。

我将以下代码作为类定义的一部分（为简洁起见，省略了其余的类定义）：

from itertools import tee

class ParsedFile():
    def __init__(self, filename):
        self.filename = filename
    def __enter__(self):
        self.file = open(self.filename)
        return self
    def __exit__(self, cls, err, tb):
        self.file.close()
        if err is not None:
            return False
    def __iter__(self):
        try:
            # spin off a new iterator for yielding
            # so the existing one isn't consumed
            self._ifile, i = tee.(self._ifile)
        except AttributeError:
            # two iterators: one to be stored
            # and spin out a new one for yielding
            self._ifile, i = tee.(iter(self._file))
        # yield results from new iterator
        yield from i
    def __len__(self):
        try:
            # assume length has already been calculated
            return self._len
        except AttributeError:
            # need to calculate length for the first time
            for ind,_ in enumerate(self):
                pass
            self._len = ind + 1
            # This line violates DRY:
            return self._len

这似乎运作良好。

但是，我的__iter__方法违反了DRY原则。我并不过分担心和＃34; pythonic＆＃34;将此视为我的设计可能存在缺陷/可以改进的信号。我能想出的唯一选择是添加while循环。

    def __len__(self):
        while True:
            try:
                # assume length has already been calculated
                return self._len
            except AttributeError:
                # need to calculate length for the first time
                for ind,_ in enumerate(self):
                    pass
                self._len = ind + 1

我担心以这种方式这样做可能导致不可预见的错误，而且只是感觉马虎。有没有更好的方法可以重做工作以避免重复？是否有充分的理由避免上述while循环解决方案？

在try中避免DRY违规：except：block

0 个答案: