Context-managed, iterable, in-memory file

memory_file.py

from StringIO import StringIO


class MemoryFile(StringIO):
    """
    This abstraction provides context management and line-iteration over the
    built-in StringIO class, making it more fully behave like a file object.
    Unfortunately, iteration is not (yet?) memory-efficient for large files.
    """
    def __init__(self, text=''):
        StringIO.__init__(self, text)
        self.lines = None
        self.index = 0

    def __iter__(self):
        self.lines = self.getvalue().split('\n')
        return self

    def next(self):
        index = self.index
        self.index += 1
        try:
            return self.lines[index]
        except IndexError:
            raise StopIteration

    def __enter__(self):
        return self

    def __exit__(self, *args):
        return True