A fractal picture - John Zells graphics.py
(When) is it better to replace comments with longer descriptive variable and function names?


That's one of the finer arts of programming, and varies by language. Much of the time, code should be clear enough and variable names sensible enough that comments are rarely needed, except for in the important places like method docstrings (which should exist regardless).

Since Python is not a strongly-typed language, it needs a little bit of encouragement to add type information, but it can still be (kind of) done via PEP484. Doing this will further enhance your ability to understand the code without needing to rely on explanatory comments. For example (these are only educated guesses):

def brushes(win: GraphWin, center_x: int, center_y: int, brush_max_radius: float):


Note the underscore convention for Python variable names.


  Does this code make sense to you?


I mean... not really? But that's just because I don't understand the fractal algorithm.

Some of the variable names are not English - koordinat? Since most of your other names are English, you should make this English, too. Some people argue that English is the universal language of development. I'm less convinced, but at least you should be internally consistent.

brushes is a confusing name. A method name should be an action - perhaps draw_brushes.

Another trick to get shorter, but still understandable, variable names - drop redundant information. windowwidth is the only width in your code, and it's used right next to the place where it's called, so call it simply WIDTH (capitals because it's a constant).


  Would it be better off with comments?


Yes, definitely - but only comments that are useful.

A comment like this:

# spiral revolutions
spiral_revolutions = 10*pi


is useless. However, a comment like this is very important and useful:

"""
This is an implementation of the fractal algorithm xxx from chapter
yyy of Zells' Python Programming.

:param win: The window object to which the fractal will be drawn.
:param center_x: The x-coordinate of the fractal's origin, in window space. 
:param center_y: The y-coordinate of the fractal's origin, in window space.
:param brush_max_radius: The maximum radius of the circles constituting the fractal.
"""