Python etree control empty tag format

Question

When creating an XML file with Python\'s etree, if we write to the file an empty tag using SubElement, I get:

Answer 1

Paraphrasing the code, the version of ElementTree.py I use contains the following in a _write method:

write('<' + tagname)
...
if node.text or len(node): # this line is literal
    write('>')
    ...
    write('' % tagname)
else:
    write(' />')

To steer the program counter I created the following:

class AlwaysTrueString(str):
    def __nonzero__(self): return True
true_empty_string = AlwaysTrueString()

Then I set node.text = true_empty_string on those ElementTree nodes where I want an open-close tag rather than a self-closing one.

By "steering the program counter" I mean constructing a set of inputs—in this case an object with a somewhat curious truth test—to a library method such that the invocation of the library method traverses its control flow graph the way I want it to. This is ridiculously brittle: in a new version of the library, my hack might break—and you should probably treat "might" as "almost guaranteed". In general, don't break abstraction barriers. It just worked for me here.