lxml 包含相对路径

Question

使用 Python 的 lxml 库，我正在尝试加载 .xsd 作为模式。 Python 脚本在一个目录中，模式在另一个目录中：

/root
    my_script.py
    /data
        /xsd
            schema_1.xsd
            schema_2.xsd

问题是 schema_1.xsd 包括 schema_2.xsd 这样的：

<xsd:include schemaLocation="schema_2.xsd"/>

作为schema_2.xsd相对路径（两个模式在同一个目录中），lxml找不到它并且它上升并出现错误：

schema_root = etree.fromstring(open('data/xsd/schema_1.xsd').read().encode('utf-8'))
schema = etree.XMLSchema(schema_root)

--> xml.etree.XMLSchemaParseError: Element '{http://www.w3.org/2001/XMLSchema}include': Failed to load the document './schema_2.xsd' for inclusion

如何在不更改架构文件的情况下解决此问题？

Answer 1

一种选择是使用 XML Catalog. You could also probably use a custom URI Resolver，但我一直使用目录。非开发人员更容易进行配置更改。如果您交付的是可执行文件而不是普通的 Python.

，这将特别有用

Windows 和 Linux 使用目录的方式不同； see here for more info。

这是一个使用 Python 3.#.

的 Windows 示例

XSD#1 (schema_1.xsd)

<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" elementFormDefault="qualified">
  <xs:include schemaLocation="schema_2.xsd"/>

  <xs:element name="doc">
    <xs:complexType>
      <xs:sequence>
        <xs:element ref="test"/>
      </xs:sequence>
    </xs:complexType>
  </xs:element>
  <xs:element name="test" type="test"/>
</xs:schema>

XSD#2 (schema_2.xsd)

<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" elementFormDefault="qualified">
    <xs:simpleType name="test">
        <xs:restriction base="xs:string">
            <xs:enumeration value="Hello World"/>
        </xs:restriction>
    </xs:simpleType>
</xs:schema>

XML 目录 (catalog.xml)

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE catalog PUBLIC "-//OASIS//DTD XML Catalogs V1.1//EN" "http://www.oasis-open.org/committees/entity/release/1.1/catalog.dtd">
<catalog xmlns="urn:oasis:names:tc:entity:xmlns:xml:catalog">
    <!-- The path in @uri is relative to this file (catalog.xml). -->
    <system systemId="schema_2.xsd" uri="./xsd_test/schema_2.xsd"/>
</catalog>

Python

import os
from urllib.request import pathname2url
from lxml import etree

# The XML_CATALOG_FILES environment variable is used by libxml2 (which is used by lxml).
# See http://xmlsoft.org/catalog.html.
if "XML_CATALOG_FILES" not in os.environ:
    # Path to catalog must be a url.
    catalog_path = f"file:{pathname2url(os.path.join(os.getcwd(), 'catalog.xml'))}"
    # Temporarily set the environment variable.
    os.environ['XML_CATALOG_FILES'] = catalog_path

schema_root = etree.fromstring(open('xsd_test/schema_1.xsd').read().encode('utf-8'))
schema = etree.XMLSchema(schema_root)

print(schema)

打印输出

<lxml.etree.XMLSchema object at 0x02B4B3F0>

Answer 2

您的情况可能还有更简单的解决方案。我今天运行解决了这个问题，并通过在导入 xml 模式时临时更改当前工作目录解决了这个问题：

import os

from lxml import etree

xml_schema_path = 'data/xsd/schema_1.xsd'

# Get the working directory the script was run from
run_dir = os.getcwd()

# Set the working directory to the schema dir so relative imports resolve from there
os.chdir(os.path.dirname(xml_schema_path))

# Load the schema. Note that you can use the `file=` option to point to a file path
xml_schema = etree.XMLSchema(file=os.path.basename(xml_schema_path))

# Re-set the working directory
os.chdir(run_dir)

lxml 包含相对路径

lxml include relative path

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xsd

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