Size of Turtle Canvas

From what I remember it is configurable. So you can set it to whatever size you want.

>>> screen.screensize()
(400, 300)
>>> screen.screensize(2000,1500)
>>> screen.screensize()
(2000, 1500)

https://docs.python.org/3.3/library/turtle.html?highlight=turtle#turtle.screensize

As for the default value, according to the docs,
turtle.screensize(canvwidth=None, canvheight=None, bg=None)
it looks like the canvas will have no size if you do not set it.