relations

[frank dilorenzo]

I have tried several different ways but I cannot seem to get this right.  What I have is a list

of suppliers.  Each supplier can have many shipments and each shipment can have many species.  Seems simple enough but apparently I must be more simple.

I need a suggestion of how to relate these table.

a supplier can have many shipment.  A shipment can have many species.  Any help would be appreciated.  Thanks.

[bnmng]

I would start by defining Supplier in your models.py, then Shipment with a ForeignKey reference to Supplier

I'm assuming (forgive me if I'm wrong) that not only can a shipment have many species, but a species can be in many shipments, so if that's the case, the most obvious way is to go with ManyToMany for that relationship

https://docs.djangoproject.com/en/4.0/topics/db/examples/many_to_many/

class Supplier(models.Model):
    (etc..etc..)

class Shipment(models.Model):
    supplier = models.ForeignKey(
        Supplier,
        on_delete=models. (...etc.. etc...)

class Species(models.Model):
    shipment = models.ManyToManyField(
        Shipment,
        (etc..)

[frank dilorenzo]

Thank you so much.  Have a great day!

frank-

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[frank dilorenzo]

After trying the suggestions I get these errors.

supplier.models:

class Supplier(models.Model):

    name = models.CharField(max_length=50)

    phone = models.CharField(max_length=15, null=True, blank=True)

    email = models.CharField(max_length=120, null=True, blank=True)

    country = models.CharField(max_length=120, null=True, blank=True)

    address = models.CharField(max_length=120, null=True, blank=True)

    city = models.CharField(max_length=120, null=True, blank=True)

    state = models.CharField(max_length=120, null=True, blank=True)

    zipCode = models.CharField(max_length=10, null=True, blank=True)

    def __str__(self):

        return self.name

shipment.models:

----------------

from django.db import models

from specie.models import Specie

from supplier.models import Supplier

# Create your models here.

class Shipment(models.Model):

    created = models.DateTimeField()

    specie = models.ManyToManyField(Specie)

    label = models.CharField(max_length=10)

    received = models.PositiveIntegerField()

    bad = models.PositiveIntegerField(default=0)

    non = models.PositiveIntegerField(default=0)

    doa = models.PositiveIntegerField(default=0)

    para = models.PositiveIntegerField(default=0)

    released = models.PositiveIntegerField(default=0)

    entered = models.BooleanField(default=False)

    supplier = models.ForeignKey(Supplier, on_delete=models.DO_NOTHING)

    def __str__(self):

        return self.supplier

    class Meta:

        ordering = ["label"]

    def __str__(self):

        return self.label

# =================================#

When I add the line supplier = models.ForeignKey(Supplier, on_delete=models.DO_NOTHING)

I get this error:

File "/Users/frankd/django_projects/Insectarium/src/shipment/models.py", line 4, in <module>

    from supplier.models import Supplier

  File "/Users/frankd/django_projects/Insectarium/src/supplier/models.py", line 3, in <module>

    from shipment.models import Shipment

ImportError: cannot import name 'Shipment' from partially initialized module 'shipment.models' (most likely due to a circular import) (/Users/frankd/django_

specie.models:

--------------

from django.db import models

from django.utils import timezone

from ckeditor.fields import RichTextField

from shipment.models import Shipment

# Create your models here.

class Specie(models.Model):

    scientific_name = models.CharField(max_length=50)

    common_name = models.CharField(max_length=50, blank=True, null=True)

    description = RichTextField(blank=True, null=True)

    image = models.ImageField(

        upload_to="specie/images/species", default="no_picture.png"

    )

    shipment = models.ManyToManyField(Shipment)

    created = models.DateField(default=timezone.now)

    def __str__(self):

        return self.scientific_name

    class Meta:

        ordering = [

            "scientific_name",

        ]

    def __str__(self):

        return self.scientific_name

# ====================== #

when I add the line shipment = models.ManyToManyField(Shipment)

I get this error.

File "<frozen importlib._bootstrap>", line 241, in _call_with_frames_removed

  File "/Users/frankd/django_projects/Insectarium/src/shipment/models.py", line 3, in <module>

    from specie.models import Specie

  File "/Users/frankd/django_projects/Insectarium/src/specie/models.py", line 5, in <module>

    from shipment.models import Shipment

ImportError: cannot import name 'Shipment' from partially initialized module 'shipment.models' (most likely due to a circular import) (/Users/frankd/django_

I think I tried this before but couldn't resolve these errors. Any suggestions would be appreciated.

frank-

[bnmng]

Hi,  

You shouldn't have to import since the models are in the same models.py  

[frank dilorenzo]

Well my friend, the only reason I have to do the imports is because each model is in it's own app. In every example I have seen the models are usually  small and contained in one app.

Perhaps I need to redesign my project to have everything lumped together?

In my project I have an app for base, shipment, supplier, species, and user.  Each app has its own rules of operations, meaning each has its own css, templates etc. 

I have looked at example until I am blue in the face but I cannot seem to get past the "cannot import name 'Supplier' from partially initialized module 'supplier.models' (most likely due to a circular import) (/Users/frankd/django" error.

I'm not sure what the "partially initialized" is telling me.

frank-

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[frank dilorenzo]

After numerous attempts I think I found my solution. (NO ERRORS)

supplier/models.py

------------------------

    shipment = models.ForeignKey(

        Shipment, on_delete=models.DO_NOTHING, null=True, blank=True)

specie/models.py 

----------------

no reference to any other model

supplier/models.py

-------------------

    specie = models.ManyToManyField(Specie)

Thanks for all the suggestions.

frank-