How to edit minor ticks in points() plot

edit

You can modify the aspect of the graphic through options of points (or point2d) or through the show method. Try this, for example:

sage: p = points([CDF(a // 5 - 3 + (a % 5 - 2)*i) for a in range(0, 35)], 
....: color="gray", marker="s", size=25)
sage: p.show(ticks=[[-3..3],None])

For a list of the graphic properties than can be changed through show options, type:

sage: p.SHOW_OPTIONS

For help about options, like color, marker or size, you can directly provide, type:

sage: point2d?

See also the documentation for points and graphics objects.

EDIT: Some graphic properties can be modified by changing matplotlib rcParams. This is the case of ticks size. Try the following code:

from matplotlib import rcParams, rcdefaults
from matplotlib.ticker import NullFormatter
rcParams['xtick.major.size'] = rcParams['xtick.minor.size'] = 0
rcParams['ytick.major.size'] = rcParams['ytick.minor.size'] = 0

points_dict = dict(color='red', size=25, marker='s', zorder=3)
grid_dict = dict(color='#AAABB8', linestyle='-')
show_dict = dict(ticks=[[-3..3],[-2..2]], tick_formatter=2*[NullFormatter()], 
                 gridlines=True, gridlinesstyle=grid_dict, aspect_ratio=1)
p = points([CDF(a // 5 - 3 + (a % 5 - 2)*I) for a in range(0, 35)], **points_dict)
p.show(**show_dict)

rcdefaults() # Just for comparison, reset rcParams...
p.show()     # ... and show points again with no particular option

The option zorder=3 included in points_dict serves to print points over the axes and gridlines. Check what happens without this option or using a lesser value.