[FIXED] How to fix circular importing?

Issue

It seems I have a circular importing error. I currently just struggling to fix it. Does anyone know what I should do?

In my models.py, containing ReservedItems & Order:

def reserveditem_pre_save_receiver(sender, instance, **kwargs):
    if not instance.order_reference:
        instance.order_reference = unique_order_reference_generator()

In my utils.py

from lumis.utils import get_random_string
from .models import Order, ReservedItem


def unique_order_reference_generator():

    new_id = get_random_string(length=10)

    reserved_item = ReservedItem.objects.filter(
        order_reference=new_id
    ).exists()
    order = Order.objects.filter(order_reference=new_id).exists()

    if reserved_item or order:
        return unique_order_reference_generator()
    else:
        return new_id

Solution

You can import modules locally in the body of the function, so:

from lumis.utils import get_random_string


def unique_order_reference_generator():
    from .models import Order, ReservedItem

    new_id = get_random_string(length=10)

    reserved_item = ReservedItem.objects.filter(
        order_reference=new_id
    ).exists()
    order = Order.objects.filter(order_reference=new_id).exists()

    if reserved_item or order:
        return unique_order_reference_generator()
    else:
        return new_id

This thus means that the module is not loaded when Python loads the file, but when the function is actually called. As a result, we can load the unique_order_reference_generator function, without having to load a the module that actually depends on this function.

Note that, like @Alasdair says, signals are typically defined in a dedicated file (signals.py) for example which should be loaded in the ready() function of the app. But regardless how you structure code, frequently local imports should be used to avoid circular imports.

Answered By - Willem Van Onsem