I use similar cases but for .NET methods. First of all Python str(["one", "two", "three"]) returns a string but not string array. Unfortunately TestComplete does not support installing and using 3rd party packages and that is their bad. The only solution I found to make sure such the cases will be working is to create own adapter between Python in TestComplete and generic/custom libraries so your pass simple string to the adapter and it convert it to whatever you need and pass to generic/library.
You can post what numPy produces for your case (or code that produce it) and maybe it is feasible in TestComplete