Without knowing more about the problem domain, it's hard to answer your question.
Unless you are certain that you need to do something more, the pythonic way to initialize a list is:
verts = []
Are you actually seeing a performance problem? If so, what is the performance bottleneck?
Don't try to solve a problem that you don't have. It's likely that performance cost to dynamically fill an array to 1000 elements is completely irrelevant to the program that you're really trying to write.
The array class is useful if the things in your list are always going to be a specific primitive fixed-length type (e.g. char, int, float). But, it doesn't require pre-initialization either.
