Python-SAX解析器：resolveEntity

Question

我很难弄清楚如何将自己的ResolveEntityHandler绑定到SAX解析器。就这样this answer。但不幸的是，我无法重现那里的结果。你知道吗

当我运行下面的代码时，它实际上是从前面的答案复制过来的，刚刚更新到Python3

import io
import xml.sax
from xml.sax.handler import ContentHandler

# Inheriting from EntityResolver and DTDHandler is not necessary
class TestHandler(ContentHandler):

    # This method is only called for external entities. Must return a value.
    def resolveEntity(self, publicID, systemID):
        print ("TestHandler.resolveEntity(): %s %s" % (publicID, systemID))
        return systemID

    def skippedEntity(self, name):
        print ("TestHandler.skippedEntity(): %s" % (name))

    def unparsedEntityDecl(self, name, publicID, systemID, ndata):
        print ("TestHandler.unparsedEntityDecl(): %s %s" % (publicID, systemID))

    def startElement(self, name, attrs):
        summary = attrs.get('summary', '')
        print ('TestHandler.startElement():', summary)

def main(xml_string):
    try:
        parser = xml.sax.make_parser()
        curHandler = TestHandler()
        parser.setContentHandler(curHandler)
        parser.setEntityResolver(curHandler)
        parser.setDTDHandler(curHandler)

        stream = io.StringIO(xml_string)
        parser.parse(stream)
        stream.close()
    except xml.sax.SAXParseException as e:
        print ("ERROR %s" % e)

XML = """<!DOCTYPE test SYSTEM "test.dtd">
<test summary='step: &num;'>Entity: &not;</test>
"""

main(XML)

以及外部的test.dtd

<!ENTITY num "FOO">
<!ENTITY pic SYSTEM 'bar.gif' NDATA gif>

我得到的是

TestHandler.startElement(): step: 
TestHandler.skippedEntity(): not

Process finished with exit code 0

所以我的问题是：

1. 为什么resolveEntity从未被调用？你知道吗
2. 如何将ResolveEntityHandler绑定到解析器？你知道吗

Answer 1

你看到的与change in Python 3.7.1有关：

Changed in version 3.7.1: The SAX parser no longer processes general external entities by default to increase security. Before, the parser created network connections to fetch remote files or loaded local files from the file system for DTD and entities. The feature can be enabled again with method setFeature() on the parser object and argument feature_external_ges.

要获得与早期版本相同的行为，请添加以下行：

from xml.sax.handler import feature_external_ges

和（在main函数中）

parser.setFeature(feature_external_ges, True)