python - Python 3 中解析 XML 模式的 LXML 问题

Question

我正在尝试使用 XRDTools 库将 Panalytical XRDML 文件转换为更适合数据库的格式，例如 pandas 数据框。

XRDTools 库的描述如下:https://github.com/paruch-group/xrdtools 。它将 XRDML 文件导入到 Python 字典中。我对 LXML 完全陌生，所以如果这是一个简单的问题，我深表歉意。

我使用 Anaconda 创建了专门用于 XRDTools 包的 Python 2.7 和 3.6 环境。我想在 Python 3.6 中运行它。

在Python 2.7中，这段代码运行顺利:

import xrdtools
xrd = xrdtools.read_xrdml('filename.xrdml')

输出是一个字典:

{u'2Theta': array([63.        , 63.00334225, 63.00668449, ..., 67.99331551,
        67.99665775, 68.        ]),
 u'Lambda': 1.540598,
 u'Omega': array([31.        , 31.00200535, 31.0040107 , ..., 33.9959893 ,
        33.99799465, 34.        ]), ...

然后我可以像任何其他 Python 对象一样使用该字典。

在 Python 3.6 中，相同的代码会生成以下错误消息:

Traceback (most recent call last):

  File "...\AppData\Local\Continuum\Anaconda2\envs\py36xrd\lib\site-packages\IPython\core\interactiveshell.py", line 2910, in run_code
    exec(code_obj, self.user_global_ns, self.user_ns)

  File "<ipython-input-3-b6f5409b8bf9>", line 1, in <module>
    xrd = xrdtools.read_xrdml('filename.xrdml')

  File "...\XRDTools\xrdtools\xrdtools\io.py", line 297, in read_xrdml
    valid = validate_xrdml_schema(filename)

  File ...\XRDTools\xrdtools\xrdtools\io.py", line 43, in validate_xrdml_schema
    xmlschema_doc = etree.parse(f)

  File "src\lxml\etree.pyx", line 3444, in lxml.etree.parse (src\lxml\etree.c:83171)

  File "src\lxml\parser.pxi", line 1855, in lxml.etree._parseDocument (src\lxml\etree.c:121011)

  File "src\lxml\parser.pxi", line 1875, in lxml.etree._parseFilelikeDocument (src\lxml\etree.c:121294)

  File "src\lxml\parser.pxi", line 1770, in lxml.etree._parseDocFromFilelike (src\lxml\etree.c:120078)

  File "src\lxml\parser.pxi", line 1185, in lxml.etree._BaseParser._parseDocFromFilelike (src\lxml\etree.c:114806)

  File "src\lxml\parser.pxi", line 598, in lxml.etree._ParserContext._handleParseResultDoc (src\lxml\etree.c:107724)

  File "src\lxml\parser.pxi", line 709, in lxml.etree._handleParseResult (src\lxml\etree.c:109433)

  File "src\lxml\parser.pxi", line 638, in lxml.etree._raiseParseError (src\lxml\etree.c:108287)

  File "...\XRDTools\xrdtools\xrdtools\data\schemas\XRDMeasurement15.xsd", line 1
    <?xml version="1.0" encoding="UTF-8"?>
                                          ^
XMLSyntaxError: Start tag expected, '<' not found, line 1, column 1

深入研究io.py，有这个函数:

def validate_xrdml_schema(filename):
    """Validate the xml schema of a given file.

    Parameters
    ----------
    filename : str
        The Filename of the `.xrdml` file to test.

    Returns
    -------
    float or None
        Returns the version number as float or None if
        the file was not matching any provided xml schema.

    """
    schemas = [(1.5, 'data/schemas/XRDMeasurement15.xsd'),
               (1.4, 'data/schemas/XRDMeasurement14.xsd'),
               (1.3, 'data/schemas/XRDMeasurement13.xsd'),
               (1.2, 'data/schemas/XRDMeasurement12.xsd'),
               (1.1, 'data/schemas/XRDMeasurement11.xsd'),
               (1.0, 'data/schemas/XRDMeasurement10.xsd'),
               ]
    schemas = [(v, os.path.join(package_path, schema)) for v, schema in schemas]

    with open(filename, 'r') as f:
        data_xml = etree.parse(f)

    for version, schema in schemas:
        with open(schema, 'r') as f:
            xmlschema_doc = etree.parse(f)
            xmlschema = etree.XMLSchema(xmlschema_doc)

        valid = xmlschema.validate(data_xml)
        if valid:
            return version
    return None

据我所知，xmlschema_doc = etree.parse(f) 导致了问题。如果我将该行更改为 etree.parse(filename)，它将运行而不会出现错误，但我不确定这是否重要。除了 Jupyter 笔记本中的小型独立单元之外，我还无法将该修复应用于任何其他内容。

什么原因导致错误？有没有办法修复 Python 3 的问题？实现该修复的最佳方法是什么？

很想解决这个问题。 TIA!

我能找到的最相关的问题: Python 3.4 lxml.etree: Start tag expected, '<' not found, line 1, column 1

Answer 1

尝试:

with io.open(filename, 'r', encoding='utf8') as f:
    data_xml = etree.parse(f)

(io.open，因为它对于 Python 2 和 Python 3 都是相同的调用)。