[Answered ]-Python/Django circular dependency with models.py (NOT in ForeignKey.etc)

Your get_future_shifts() method implies that Shift has a FK on Mentor. In this case, you don’t need to import Shift in the module containing Mentor, you can just use the reverse relationship ie:

class Mentor(models.Model):
    # ...
    def get_future_shifts(self):
        return self.shift_set.filter(session__date__gt=timezone.now())

but this will only “technically” solve the circular dependency, since it means that Mentor has some direct knowledge of another app that itself depends on the app where Mentor is defined and the whole thing will break if you remove this other app from your settings.

Another solution is to define get_future_shifts in the same app as Shift' and monkeypatchMentor`, ie:

from otherapp.models import Mentor

class Shift(models.Model):
    mentor = models.ForeignKey(Mentor)

# Extend Mentor with get_future_shifts helper    
def get_future_shifts(mentor):
    return mentor.shift_set.filter(session__date__gt=timezone.now())

Mentor.get_future_shifts = get_future_shifts

Some will frown upon extending a class from another module / app, but just defining a FK on Mentor here is already extending Mentor, so at least we keep related stuff together and now Mentor has no direct dependency on Shift – as long as nothing in Mentor‘s app’s views etc depends on get_future_shifts() at least, but then it means that Shifts should really belong to the same app as Mentor.