Comtypes depends on numpy for wstring[] attributes

[cfarrow]

From the mailing list: http://sourceforge.net/p/comtypes/mailman/message/32392260/

I've just hit an issue using comtypes to interact with Virtualbox.
Here's the simplest test case I can create:

import comtypes.client
import comtypes.gen.VirtualBox

vbox = comtypes.client.CreateObject('VirtualBox.VirtualBox')
machine = vbox.FindMachine('Ahri')
adapter = machine.getNetworkAdapter(0)
nat = adapter.NATEngine
print(repr(nat.redirects))

This gets the redirects property from the NatEngine object, which is
documented as follows:

readonly attribute wstring[] redirects
Array of NAT port-forwarding rules in string representation, in the
following format: "name,protocol id,host ip,host port,guest ip,guest
port".

When I run this test, I get:

python .\test.py
Traceback (most recent call last):
File ".\test.py", line 8, in
print(repr(nat.redirects))
File "C:\Work\Projects\vm\ve\lib\site-packages\comtypes__init__.py",
line 279, in getattr
return getattr(self, fixed_name)
File "C:\Work\Projects\vm\ve\lib\site-packages\comtypes\safearray.py",
line 218, in ctypes_from_outparam
return self[0]
File "C:\Work\Projects\vm\ve\lib\site-packages\comtypes\safearray.py",
line 209, in getitem
return self.unpack()
File "C:\Work\Projects\vm\ve\lib\site-packages\comtypes\safearray.py",
line 234, in unpack
result = self._get_elements_raw(num_elements)
File "C:\Work\Projects\vm\ve\lib\site-packages\comtypes\safearray.py",
line 301, in _get_elements_raw
import numpy.ctypeslib
ImportError: No module named 'numpy'

As far as I can tell, comtypes is interpreting the array of wstring
objects as a 2-dimensional array, and as a result thinks it needs
numpy.

Two suggestions here:

1. If numpy isn't available, fall back to something core Python can
   handle like a tuple of tuples.
2. In this particular case, the code should be returning a tuple of
   (Unicode) strings.

The equivalent code works with pywin32, for what it's worth.

[pfmoore]

See PR #56. It seems to fix the issue for me, but I don't follow the refcounting semantics in comtypes so it's possible I've introduced a memory leak or similar. So a review by someone who actually understands the code would be useful!

[cfarrow]

@pfmoore, please try out #59 (branch bstr-array-redux). It should accomplish the same as #56 and fix the import issue.

[pfmoore]

Yep, that works for me. Many thanks!

[cfarrow]

Excellent. Thanks for the report and initial patch.