Django: RecursionError: maximum recursion depth exceeded

Question

I am getting a runtime error in django while saving a certain model.

I want to save the model with two instances

So I have done the following:


class Journal(models.Model):
    user = models.ForeignKey(
        settings.AUTH_USER_MODEL, on_delete=models.CASCADE, null=True, blank=True
    )
    company = models.ForeignKey(
        company, on_delete=models.CASCADE, null=True, blank=True, related_name="Companyname"
    )
    counter = models.IntegerField(blank=True, null=True)
    urlhash = models.CharField(max_length=100, null=True, blank=True, unique=True)
    date = models.DateField(default=datetime.date.today)
    voucher_id = models.PositiveIntegerField(blank=True, null=True)
    voucher_type = models.CharField(max_length=100, blank=True)
    by = models.ForeignKey(ledger1, on_delete=models.CASCADE, related_name="Debitledgers")
    to = models.ForeignKey(ledger1, on_delete=models.CASCADE, related_name="Creditledgers")
    debit = models.DecimalField(max_digits=10, decimal_places=2, null=True)
    credit = models.DecimalField(max_digits=10, decimal_places=2, null=True)
    narration = models.TextField(blank=True)


@receiver(pre_save, sender=Journal)
def pl_journal(sender, instance, *args, **kwargs):
    if (
        instance.debit != None
        or instance.credit != None
        or instance.by.group1_Name.group_Name == "Indirect Expense"
    ):
        Journal.objects.update_or_create(
            user=instance.user,
            company=instance.company,
            date=instance.date,
            voucher_id=instance.id,
            voucher_type="Journal",
            by=instance.by,
            to=ledger1.objects.filter(
                user=instance.user, company=instance.company, name__icontains="Profit & Loss A/c"
            ).first(),
            debit=instance.debit,
            dredit=instance.credit,
        )

The problem is in the following line of code in my signal:

to=ledger1.objects.filter(user=instance.user,company=instance.company,name__icontains='Profit & Loss A/c').first()

Anyone have any idea why this error is happening?

Is there any way to solve it?

Thank you

Can you explain what you are actually trying to achieve, though? — AKX
– AKX, Commented Mar 6, 2019 at 12:42
I want to save two instance of journal object whenever a journal object is created for example if a by object in journal is created under instance.by.group1_Name.group_Name == "Indirect Expense" it will trigger the signal to create another instance of journal model as given in the signal. — Niladry Kar
– Niladry Kar, Commented Mar 6, 2019 at 12:47
I guess the Journal object you're creating matches in the pre_save signal matches the condition in the signal, so it gets called recursively. — AKX
– AKX, Commented Mar 6, 2019 at 12:49
There's not much you can do than, well, not do that. For example, you could add a field to the model that you'd check and prevent "re-handling" it in the hook. — AKX
– AKX, Commented Mar 6, 2019 at 13:20

AKX · Accepted Answer · 2019-03-06 12:37:17Z

2

You have a pre_save signal receiver for a model that ends up managing the same model, so you get something like this:

journal.save() is called
pl_journal(sender=Journal, instance=journal) is called
Journal.objects.update_or_create(...) is (possibly) called
.update_or_create() calls .save() on the Journal instance it updates or creates, so go back to step 1.

You thus have an infinite recursion happening, which Python limits to the maximum recursion depth and raises that exception.

answered Mar 6, 2019 at 12:37

AKX

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