How to conditionally insert an attribute into a node in Python using xml.etree.ElementTree

Question

I'm building an XML document using Python's xml.etree.ElementTree and am unable to conditionally insert an attribute into a node. Here's an example of my code:

Attr1="stamps"
Attr2="ghouls"
Attr3=""   

node = ET.SubElement(root_node, "ChildNode1",
                         Attr1=Attr1,
                         Attr2=Attr2,
                         Attr3=Attr3)

Simple enough, output is exactly as expected. However, many XML documents I've seen exclude the attribute entirely if the value is None. How do I do this? Something like:

Attr1="stamps"
Attr2="ghouls"
Attr3=""   

node = ET.SubElement(root_node, "ChildNode1",
                         Attr1=Attr1,
                         Attr2=Attr2,
                         (Attr3=Attr3 if Attr != "" else pass))

But this syntax is not supported by the library. I know I can do an if statement and copy the code over for the entire node minus the conditional value, but I do not want to duplicate code many times over. Is there a quick and easy way to do this using the ElementTree library?

Answer 1

Just create the element first, and then add the attribute afterwards

node = ET.SubElement(root_node,"ChildNode1",Attr1=Attr1,Attr2=Attr2)
if Attr3 != "":
    node.attrib["Attr3"] = Attr3

The same approach can be done with Attr1 and Attr2 if you are concerned about those being empty.

ElementTree keeps all of the attributes of an element in a dictionary available in the attrib attribute of the object. The keys are the attribute names and the values are the attribute values.

Answer 2

Creating a dictionary is an easy way to manipulate the keyword arguments.

attrs = {}

attrs["Attr1"] = "stamps"
attrs["Attr2"] = "ghouls"
if Attr != "":
    attrs["Attr3"] = Attr

node = ET.SubElement(root_node, "ChildNode1", **attrs)