python - 使用 LXML 编写 XML header

Question

我目前正在编写一个脚本，将一堆 XML 文件从各种编码转换为统一的 UTF-8。

我首先尝试使用 LXML 确定编码:

def get_source_encoding(self):
    tree = etree.parse(self.inputfile)
    encoding = tree.docinfo.encoding
    self.inputfile.seek(0)
    return (encoding or '').lower()

如果那是空白，我会尝试从 chardet 获取它:

def guess_source_encoding(self):
    chunk = self.inputfile.read(1024 * 10)
    self.inputfile.seek(0)
    return chardet.detect(chunk).lower()

然后我使用codecs 来转换文件的编码:

def convert_encoding(self, source_encoding, input_filename, output_filename):
    chunk_size = 16 * 1024

    with codecs.open(input_filename, "rb", source_encoding) as source:
        with codecs.open(output_filename, "wb", "utf-8") as destination:
            while True:
                chunk = source.read(chunk_size)

                if not chunk:
                    break;

                destination.write(chunk)

最后，我正在尝试重写 XML header 。如果 XML header 最初是

<?xml version="1.0"?>

或

<?xml version="1.0" encoding="windows-1255"?>

我想把它变成

<?xml version="1.0" encoding="UTF-8"?>

我当前的代码似乎不起作用:

def edit_header(self, input_filename):
    output_filename = tempfile.mktemp(suffix=".xml")

    with open(input_filename, "rb") as source:
        parser = etree.XMLParser(encoding="UTF-8")
        tree = etree.parse(source, parser)

        with open(output_filename, "wb") as destination:
            tree.write(destination, encoding="UTF-8")

我当前正在测试的文件有一个未指定编码的 header 。如何让它以指定的编码正确输出 header ？

Answer 1

尝试:

tree.write(destination, xml_declaration=True, encoding='UTF-8')

来自 the API docs :

xml_declaration controls if an XML declaration should be added to the file. Use False for never, True for always, None for only if not US-ASCII or UTF-8 (default is None).

来自 ipython 的示例:

In [15]:  etree.ElementTree(etree.XML('<hi/>')).write(sys.stdout, xml_declaration=True, encoding='UTF-8')
<?xml version='1.0' encoding='UTF-8'?>
<hi/>

---

仔细想想，我觉得你太努力了。 lxml 自动检测编码并根据该编码正确解析文件。

所以你真正需要做的(至少在 Python2.7 中)是:

def convert_encoding(self, source_encoding, input_filename, output_filename):
    tree = etree.parse(input_filename)
    with open(output_filename, 'w') as destination:
        tree.write(destination, encoding='utf-8', xml_declaration=True)