Looking at the code in sw/source/core/unocore/unotbl.cxx : 
 
uno::Any SwXTableColumns::getByIndex(sal_Int32 nIndex) 
        throw( IndexOutOfBoundsException, WrappedTargetException, uno::RuntimeException ) 
{ 
        vos::OGuard aGuard(Application::GetSolarMutex()); 
        uno::Reference< uno::XInterface >  xRet; 
        SwFrmFmt* pFrmFmt = GetFrmFmt(); 
        if(!pFrmFmt) 
                throw uno::RuntimeException(); 
        else 
        { 
                USHORT nCount = 0; 
                SwTable* pTable = SwTable::FindTable( pFrmFmt ); 
                if(!pTable->IsTblComplex()) 
                { 
                        SwTableLines& rLines = pTable->GetTabLines(); 
                        SwTableLine* pLine = rLines.GetObject(0); 
                        nCount = pLine->GetTabBoxes().Count(); 
                } 
                if(nCount <= nIndex || nIndex < 0) 
                        throw IndexOutOfBoundsException(); 
                xRet = *new cppu::OWeakObject(); 
        } 
        return uno::Any(&xRet, ::getCppuType((const uno::Reference<uno::XInterface>*)0)); 
} 
 
you can see that even though the code in the middle retrieves some information 
it does not set xRet with any value except " *new cppu::OWeakObject();" which is so  
close to 0 that it is useless :) 
 
The result of this is that when I have the following python code : 
        cols = currentTable.getColumns() 
        print  cols.getByIndex(1)  
 
I would expect to get something like : 
pyuno object (com.sun.star.beans.XPropertySet)0x82963d0 {  
        implementationName=SwXTextTableColumn,  
        supportedServices={com.sun.star.text.TextTableColumn}, supportedInterfaces= {  
        com.sun.star.beans.XPropertySet, com.sun.star.lang.XServiceInfo,  
        com.sun.star.lang.XTypeProvider, com.sun.star.uno.XWeak}} 
 
but instead I get : 
pyuno object (com.sun.star.uno.XInterface)0x82a2370{} 
 
:(