validators.py 文件源码

def __call__(self, value):

        if value is None:
            return value

        path = unicode(value)

        if not os.path.isabs(path):
            path = os.path.join(self.directory, path)

        try:
            value = open(path, self.mode) if self.buffering is None else open(path, self.mode, self.buffering)
        except IOError as error:
            raise ValueError('Cannot open {0} with mode={1} and buffering={2}: {3}'.format(
                value, self.mode, self.buffering, error))

        return value