GeoDjango: How to create a circle based on point and radius

Question

I have the following (simplified) Model:

class Zone(gismodels.Model):
    name = gismodels.CharField()
    poly = gismodels.PolygonField()

Answer 1

Yes, it is possible to use the geos buffer method:

>>> from django.contrib.gis import geos
>>> center = geos.Point(5, 5)
>>> radius = 2
>>> circle = center.buffer(radius)
>>> circle

The radius here is in the same units as the coordinates of the points. This will work for some coordinate systems like UTM, but not as well for others.

Also, while this is appropriate for constructing a circular geometry, the PostGIS documentation notes that for doing radius searches ST_DWithin is more efficient.