Unicode字符串的lxml.etree.XML ValueError

Question

我正在用an xml转换xslt文档。使用python3进行操作时，出现以下错误。但是python2没有任何错误

-> % python3 cstm/artefact.py
Traceback (most recent call last):
  File "cstm/artefact.py", line 98, in <module>
    simplify_this_dataset('fisheries-service-des-peches.xml')
  File "cstm/artefact.py", line 85, in simplify_this_dataset
    xslt_root = etree.XML(xslt_content)
  File "lxml.etree.pyx", line 3012, in lxml.etree.XML (src/lxml/lxml.etree.c:67861)
  File "parser.pxi", line 1780, in lxml.etree._parseMemoryDocument (src/lxml/lxml.etree.c:102420)
ValueError: Unicode strings with encoding declaration are not supported. Please use bytes input or XML fragments without declaration.

#!/usr/bin/env python3
# vim:fileencoding=UTF-8:ts=4:sw=4:sta:et:sts=4:ai
# -*- coding: utf-8 -*-

from lxml import etree

def simplify_this_dataset(dataset):
    """Create A simplify version of an xml file
    it will remove all the attributes and assign them as Elements instead
    """
    module_path = os.path.dirname(os.path.abspath(__file__))
    data = open(module_path+'/data/ex-fire.xslt')
    xslt_content = data.read()
    xslt_root = etree.XML(xslt_content)
    dom = etree.parse(module_path+'/../CanSTM_dataset/'+dataset)
    transform = etree.XSLT(xslt_root)
    result = transform(dom)
    f = open(module_path+ '/../CanSTM_dataset/otra.xml', 'w')
    f.write(str(result))
    f.close()

Answer 1

data = open(module_path+'/data/ex-fire.xslt')
xslt_content = data.read()

这会使用默认编码将文件中的字节隐式解码为Unicode文本。 （如果XML文件不是该编码，则可能会导致错误的结果。）

xslt_root = etree.XML(xslt_content)

XML具有自己的编码处理和信令，即<?xml encoding="..."?>序言。如果您将以<?xml encoding="..."?>开头的Unicode字符串传递给解析器，则解析器希望使用该编码来重新声明字节字符串的其余部分...但是不能，因为您已经解码了输入到Unicode的字节字符串。

相反，您应该将未解码的字节字符串传递给解析器：

data = open(module_path+'/data/ex-fire.xslt', 'rb')

xslt_content = data.read()
xslt_root = etree.XML(xslt_content)

或者更好，只是让解析器直接从文件中读取：

xslt_root = etree.parse(module_path+'/data/ex-fire.xslt')

Answer 2

您还可以在将UTF-8字符串传递给etree.XML之前对其进行解码，并使用ascii对其进行编码

 xslt_content = data.read()
 xslt_content = xslt_content.decode('utf-8').encode('ascii')
 xslt_root = etree.XML(xslt_content)

Answer 3

我通过使用默认选项简单地重新编码使它起作用

xslt_content = data.read().encode()