Add expand_iter kw to unparse to expand iterables

[claweyenuk]

Add expand_iter kwarg to unparse that will expand lists into sets of XML elements rather than outputting the string representation of the list

This is more of a proposal than actual PR - I should probably update the README and add a test. But before doing that I wanted to submit this.

Using a simple dict:

test_dict = {'root': {'imgs': ((1, 2), (3, 4))}}

Output before the change/with out the flag:

print(xmltodict.unparse(test_dict, pretty=True))
<?xml version="1.0" encoding="utf-8"?>
<root>
	<imgs>(1, 2)</imgs>
	<imgs>(3, 4)</imgs>
</root>

After:

print(xmltodict.unparse(test_dict, expand_iter="item", pretty=True))
<?xml version="1.0" encoding="utf-8"?>
<root>
	<imgs>
		<item>1</item>
		<item>2</item>
	</imgs>
	<imgs>
		<item>3</item>
		<item>4</item>
	</imgs>
</root>

[yan-hic]

Is this PR/enhancement stalled ? I have a similar requirement for a list of dicts.
Currently iterating and unparse each item, and joining the XML result. It would be cleaner - with less overhead - to do in one operation.

[martinblech]

This looks like a great addition, thanks for your contribution! Could you update the PR with tests and docs?

[claweyenuk]

No stall really. I just avoided adding tests in case this was not a useful addition.

I am a bit tight on time for the next few weeks, so I won't be able to add tests just yet. Feel free to use the code or add tests.

[claweyenuk]

Much longer than 3 weeks, but I gave this another go with tests and some documentation. Please let me know if there's anything missing/incorrect!

[claweyenuk]

@martinblech just a heads up to make sure this is on your radar

[martinblech]

Thank you so much for this contribution!