11.11 Standard Module xmllib

  

This module defines a class XMLParser which serves as the basis for parsing text files formatted in XML (eXtended Markup Language).

XMLParser ()

The XMLParser class must be instantiated without arguments.

This class provides the following interface methods:

reset ()

Reset the instance. Loses all unprocessed data. This is called implicitly at the instantiation time.

setnomoretags ()

Stop processing tags. Treat all following input as literal input (CDATA).

setliteral ()

Enter literal mode (CDATA mode).

feed (data)

Feed some text to the parser. It is processed insofar as it consists of complete elements; incomplete data is buffered until more data is fed or close() is called.

close ()

Force processing of all buffered data as if it were followed by an end-of-file mark. This method may be redefined by a derived class to define additional processing at the end of the input, but the redefined version should always call close().

translate_references (data)

Translate all entity and character references in data and returns the translated string.

handle_xml (encoding, standalone)

This method is called when the "<?xml ...?>" tag is processed. The arguments are the values of the encoding and standalone attributes in the tag. Both encoding and standalone are optional. The values passed to handle_xml() default to None and the string 'no' respectively.

handle_doctype (tag, data)

This method is called when the "<!DOCTYPE...>" tag is processed. The arguments are the name of the root element and the uninterpreted contents of the tag, starting after the white space after the name of the root element.

handle_starttag (tag, method, attributes)

This method is called to handle start tags for which a start_tag() method has been defined. The tag argument is the name of the tag, and the method argument is the bound method which should be used to support semantic interpretation of the start tag. The attributes argument is a dictionary of attributes, the key being the name and the value being the value of the attribute found inside the tag's <> brackets. Character and entity references in the value have been interpreted. For instance, for the tag <A HREF="http://www.cwi.nl/">, this method would be called as handle_starttag('A', self.start_A, {'HREF': 'http://www.cwi.nl/'}). The base implementation simply calls method with attributes as the only argument.

handle_endtag (tag, method)

This method is called to handle endtags for which an end_tag() method has been defined. The tag argument is the name of the tag, and the method argument is the bound method which should be used to support semantic interpretation of the end tag. If no end_tag() method is defined for the closing element, this handler is not called. The base implementation simply calls method.

handle_data (data)

This method is called to process arbitrary data. It is intended to be overridden by a derived class; the base class implementation does nothing.

handle_charref (ref)

This method is called to process a character reference of the form "&#ref;". ref can either be a decimal number, or a hexadecimal number when preceded by an "x". In the base implementation, ref must be a number in the range 0-255. It translates the character to ASCII and calls the method handle_data() with the character as argument. If ref is invalid or out of range, the method unknown_charref(ref) is called to handle the error. A subclass must override this method to provide support for character references outside of the ASCII range.

handle_entityref (ref)

This method is called to process a general entity reference of the form "&ref;" where ref is an general entity reference. It looks for ref in the instance (or class) variable entitydefs which should be a mapping from entity names to corresponding translations. If a translation is found, it calls the method handle_data() with the translation; otherwise, it calls the method unknown_entityref(ref). The default entitydefs defines translations for &amp;, &apos, &gt;, &lt;, and &quot;.

handle_comment (comment)

This method is called when a comment is encountered. The comment argument is a string containing the text between the "<!-" and "->" delimiters, but not the delimiters themselves. For example, the comment "<!-text->" will cause this method to be called with the argument 'text'. The default method does nothing.

handle_cdata (data)

This method is called when a CDATA element is encountered. The data argument is a string containing the text between the "<![CDATA[" and "]]>" delimiters, but not the delimiters themselves. For example, the entity "<![CDATA[text]]>" will cause this method to be called with the argument 'text'. The default method does nothing, and is intended to be overridden.

handle_proc (name, data)

This method is called when a processing instruction (PI) is encountered. The name is the PI target, and the data argument is a string containing the text between the PI target and the closing delimiter, but not the delimiter itself. For example, the instruction "<?XML text?>" will cause this method to be called with the arguments 'XML' and 'text'. The default method does nothing. Note that if a document starts with "<?xml ...?>", handle_xml() is called to handle it.

handle_special (data)

This method is called when a declaration is encountered. The data argument is a string containing the text between the "<!" and ">" delimiters, but not the delimiters themselves. For example, the entity "<!ENTITY text>" will cause this method to be called with the argument 'ENTITY text'. The default method does nothing. Note that "<!DOCTYPE ...>" is handled separately if it is located at the start of the document.

syntax_error (message)

This method is called when a syntax error is encountered. The message is a description of what was wrong. The default method raises a RuntimeError exception. If this method is overridden, it is permissable for it to return. This method is only called when the error can be recovered from. Unrecoverable errors raise a RuntimeError without first calling syntax_error().

unknown_starttag (tag, attributes)

This method is called to process an unknown start tag. It is intended to be overridden by a derived class; the base class implementation does nothing.

unknown_endtag (tag)

This method is called to process an unknown end tag. It is intended to be overridden by a derived class; the base class implementation does nothing.

unknown_charref (ref)

This method is called to process unresolvable numeric character references. It is intended to be overridden by a derived class; the base class implementation does nothing.

unknown_entityref (ref)

This method is called to process an unknown entity reference. It is intended to be overridden by a derived class; the base class implementation does nothing.

Apart from overriding or extending the methods listed above, derived classes may also define methods and variables of the following form to define processing of specific tags. Tag names in the input stream are case dependent; the tag occurring in method names must be in the correct case:

start_tag (attributes)

This method is called to process an opening tag tag. The attributes argument has the same meaning as described for handle_starttag() above. In fact, the base implementation of handle_starttag() calls this method.

end_tag ()

This method is called to process a closing tag tag.

tag_attributes

If a class or instance variable tag_attributes exists, it should be a list or a dictionary. If a list, the elements of the list are the valid attributes for the element tag; if a dictionary, the keys are the valid attributes for the element tag, and the values the default values of the attributes, or None if there is no default. In addition to the attributes that were present in the tag, the attribute dictionary that is passed to handle_starttag() and unknown_starttag() contains values for all attributes that have a default value.