Panda takes up about a constant 20-40 MB. In any modern game this is a negligible fraction of the total game size. The rest will all be your own game files. So, the game will be as large as you make it. It’s unlikely to get into gigabyte-sized programs without you adding gigabyte-sized models or textures.
Some of the errors earlier in this thread indicated you were instantiating ShowBase more than once, or importing DirectStart and instantiating ShowBase. Keep in mind that there can only be one ShowBase instance at a time.
As for this error:
base = ShowBase()
NameError: name 'Showbase' is not definedThe case doesn’t seem to match up between the quoted line of code and the error message. Note that Python is case-sensitive. It could also be that you have not imported ShowBase yet at that point.