Python 2.7 Unicode 写入器对 NoneType 的鲁棒性

Question

我希望使用UnicodeWriter，来自官方示例，这样在写CSV文件时就不会出现Unicode数据的问题。然而，如果我在应该作为一行的数据列表中有空白、缺失或NaN（不是一个数字），我就会遇到这个错误：

    self.writer.writerow([s.encode("utf-8") for s in row])
AttributeError: 'NoneType' object has no attribute 'encode'

有没有简单的解决办法呢？

我在下面重复了“官方代码”：

class UnicodeWriter:
    """
    A CSV writer which will write rows to CSV file "f",
    which is encoded in the given encoding.
    """

    def __init__(self, f, dialect=csv.excel, encoding="utf-8", **kwds):
        # Redirect output to a queue
        self.queue = cStringIO.StringIO()
        self.writer = csv.writer(self.queue, dialect=dialect, **kwds)
        self.stream = f
        self.encoder = codecs.getincrementalencoder(encoding)()

    def writerow(self, row):
        self.writer.writerow([s.encode("utf-8") for s in row])
        # Fetch UTF-8 output from the queue ...
        data = self.queue.getvalue()
        data = data.decode("utf-8")
        # ... and reencode it into the target encoding
        data = self.encoder.encode(data)
        # write to the target stream
        self.stream.write(data)
        # empty queue
        self.queue.truncate(0)

    def writerows(self, rows):
        for row in rows:
            self.writerow(row)

Answer 1

之前有个问题（虽然是关于数字的字符串转换），也解决了这个问题，看看这个回答。只需要加一个转换成unicode的步骤：self.writer.writerow([unicode(s).encode("utf-8") for s in row])