append
on list appends the item in place and does not return a new list. With the following:
elements2 = elements0.append(elements1)
elements2
being assigned the value None
and elements0
now contains a new item, which is elements1
elements0[0] -> Paragraph("The Platypus0", styles['Heading1'])
elements0[1] -> Paragraph("Very <i>Special</i>!", styles['Normal'])
elements0[2] -> [Paragraph("The Platypus1", styles['Heading1']), Paragraph("Very <i>Special</i>!", styles['Normal'])
If you want to put the two texts together, use the concatenation
elements2 = elements0 + elements1