> I have a class
> The point of this class is to provide an uncluttered interface
> to Document Creation
>
>
> from xml.dom.minidom import getDOMImplementation
>
> class NpDOMDocumentFactory:
>
> """A DOM Document Factory convenience class"""
>
>
>
> # make these private "by convention"
> __DOMImplementation = getDOMImplementation()
> __defaultNamespaceUri = "http://nuldomain.com/";
> __defaultQualifiedName = "root"
> __defaultDoctype = __DOMImplementation.createDocumentType("HTML",
> "-//W3C//DTD HTML
> 4.01//EN",
Trying to make things "private" is a throwback to Java. In Python
the tendency is to just leave everything "public". And "private" is with
one underbar/underscore.
>
> "http://www.w3.org/TR/html4/strict.dtd";)
> #params required for the createDocument method on DOMImplementation
> #DOMImplementation.createDocument(namespaceUri, qualifiedName, doctype)
>
> #get a default document with the root element initialised to
> def getDOMDocument(self):
> print("no args")
> return self.__DOMImplementation.createDocument(None, "root", None)
>
> #allow a user to specify the namespaceUri node name
> def getDOMDocument(self, namespaceUri=__defaultNamespaceUri):
> return self.__DOMImplementation.createDocument(namespaceUri, "root",
> None)
>
>
> #allow a user to specify the namespaceUri and a qualifiedName
> def getDOMDocument(self, namespaceUri=__defaultNamespaceUri,
> qualifiedName=__defaultQualifiedName):
> return self.__DOMImplementation.createDocument(namespaceUri,
> qualifiedName, None)
>
>
> #allow a user to specify the namespaceUri, a qualifiedName and a doctype
> def getDOMDocument(self, namespaceUri=__defaultNamespaceUri,
> qualifiedName=__defaultQualifiedName, docType=__defaultDoctype):
> print("3 args")
> return self.__DOMImplementation.createDocument(namespaceUri,
> qualifiedName, docType)
>
>
>
> #end NpDOMDocumentFactory
>
> factory = NpDOMDocumentFactory()
>
> print(factory.getDOMDocument().toxml())
>
> when I pass this to python I get the following
>
> lipska@ubuntu:~/python/dev/classes/com/nuldomain/xml$ python3.2
> NpDOMDocumentFactory.py
> 3 args
> 'http://www.w3.org/TR/html4/strict.dtd'>
>
> I have absolutely no idea why a method that requires three arguments is being
> called when I intend the "no args" method to be called
>
Python does not have polymorphism in the same manner as Java.
Instead of creating different methods with a different number of
arguments, you create one method with "optional" arguments, i.e.
"keyword" arguments.
def function( something=None ):
print(something)
This creates a function where the argument 'something' is optional.
If nothing is passed in, then something will default to None. If
something is passed in as either a positional or keyword argument--
func('test') or func(something='test')--then the value of something
will be whatever is passed in.
Now applying that to your method I see you have three different
return statements.
return self.__DOMImplementation.createDocument(namespaceUri,
qualifiedName, docType)
return self.__DOMImplementation.createDocument(namespaceUri,
qualifiedName, None)
return self.__DOMImplementation.createDocument(namespaceUri,
"root", None)
So I will use the method definition.
def getDOMDocument(self, namespaceUri=__defaultNamespaceUri,
qualifiedName=__defaultQualifiedName, docType=__defaultDoctype):
return self.__DOMImplementation.createDocument(namespaceUri,
qualifiedName, docType)
Now in order to get the same returns as above I will call
it with the following options.
self.getDOMDocument(namespace_url, qualified_name, doc_type )
self.getDOMDocument(namespace_url, qualified_name, docType=None )
self.getDOMDocument(namespace_url, docType=None, qualifiedName="root" )
The last line can also be written entirely as positional arguments.
self.getDOMDocument(namespace_url, "root", None )
Or if you want to use all the default arguments
self.getDOMDocument()
Ramit
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