Issue
What’s a proper way to define many-to-many relationships in a pydantic model without getting circular import error.
I have two files supplier_schema.py and category_schema.py.
supplier_schema.py
from pydantic import BaseModel, HttpUrl, EmailStr
from typing import Optional, List
from datetime import datetime
from schemas.category_schema import Category
from schemas.membership_schema import Membership
class SupplierBase(BaseModel):
contact_person: str
email_address: EmailStr
company_name: str
company_email: str
company_logo: str
country: str
state_province: str
city_area: Optional[str] = None
location: str
phone: str
fax: Optional[str] = None
tagline: str
company_bio: Optional[str]
year_established: int
employees_count: str
certificates: Optional[List[str]] = None
cover_image: Optional[HttpUrl] = None
gallery: Optional[List[HttpUrl]] = None
company_license: Optional[HttpUrl] = None
company_website: Optional[HttpUrl] = None
whatsapp_number: Optional[str] = None
facebook_url: Optional[HttpUrl] = None
twitter_url: Optional[HttpUrl] = None
linkedin_url: Optional[HttpUrl] = None
pinterest_url: Optional[HttpUrl] = None
instagram_url: Optional[HttpUrl] = None
youtube_url: Optional[HttpUrl] = None
annual_revenue: Optional[str] = None
challenges: List[str]
status: str = None
class Config:
orm_mode = True
class SupplierCreate(SupplierBase):
password: str
membership_id: int
categories_id: Optional[List[int]] = []
class Supplier(SupplierBase):
id: int
created_at: datetime
updated_at: datetime
membership: Membership
categories: List[Category]
category_schema.py
from pydantic import BaseModel, HttpUrl, EmailStr
from typing import Optional, List
from datetime import datetime
from schemas.category_schema import Category
from schemas.membership_schema import Membership
class SupplierBase(BaseModel):
contact_person: str
email_address: EmailStr
company_name: str
company_email: str
company_logo: str
country: str
state_province: str
city_area: Optional[str] = None
location: str
phone: str
fax: Optional[str] = None
tagline: str
company_bio: Optional[str]
year_established: int
employees_count: str
certificates: Optional[List[str]] = None
cover_image: Optional[HttpUrl] = None
gallery: Optional[List[HttpUrl]] = None
company_license: Optional[HttpUrl] = None
company_website: Optional[HttpUrl] = None
whatsapp_number: Optional[str] = None
facebook_url: Optional[HttpUrl] = None
twitter_url: Optional[HttpUrl] = None
linkedin_url: Optional[HttpUrl] = None
pinterest_url: Optional[HttpUrl] = None
instagram_url: Optional[HttpUrl] = None
youtube_url: Optional[HttpUrl] = None
annual_revenue: Optional[str] = None
challenges: List[str]
status: str = None
class Config:
orm_mode = True
class SupplierCreate(SupplierBase):
password: str
membership_id: int
categories_id: Optional[List[int]] = []
class Supplier(SupplierBase):
id: int
created_at: datetime
updated_at: datetime
membership: Membership
categories: List[Category]
But I get this error
Traceback (most recent call last):
File "/usr/lib/python3.9/multiprocessing/process.py", line 315, in _bootstrap
self.run()
File "/usr/lib/python3.9/multiprocessing/process.py", line 108, in run
self._target(*self._args, **self._kwargs)
File "/home/phat/projects/crdle2-api/venv/lib/python3.9/site-packages/uvicorn/subprocess.py", line 61, in subprocess_started
target(sockets=sockets)
File "/home/phat/projects/crdle2-api/venv/lib/python3.9/site-packages/uvicorn/server.py", line 49, in run
loop.run_until_complete(self.serve(sockets=sockets))
File "uvloop/loop.pyx", line 1501, in uvloop.loop.Loop.run_until_complete
File "/home/phat/projects/crdle2-api/venv/lib/python3.9/site-packages/uvicorn/server.py", line 56, in serve
config.load()
File "/home/phat/projects/crdle2-api/venv/lib/python3.9/site-packages/uvicorn/config.py", line 308, in load
self.loaded_app = import_from_string(self.app)
File "/home/phat/projects/crdle2-api/venv/lib/python3.9/site-packages/uvicorn/importer.py", line 23, in import_from_string
raise exc from None
File "/home/phat/projects/crdle2-api/venv/lib/python3.9/site-packages/uvicorn/importer.py", line 20, in import_from_string
module = importlib.import_module(module_str)
File "/usr/lib/python3.9/importlib/__init__.py", line 127, in import_module
return _bootstrap._gcd_import(name[level:], package, level)
File "<frozen importlib._bootstrap>", line 1030, in _gcd_import
File "<frozen importlib._bootstrap>", line 1007, in _find_and_load
File "<frozen importlib._bootstrap>", line 986, in _find_and_load_unlocked
File "<frozen importlib._bootstrap>", line 680, in _load_unlocked
File "<frozen importlib._bootstrap_external>", line 850, in exec_module
File "<frozen importlib._bootstrap>", line 228, in _call_with_frames_removed
File "/home/phat/projects/crdle2-api/./main.py", line 3, in <module>
from routers import supplier_router, membership_router, category_router
File "/home/phat/projects/crdle2-api/./routers/supplier_router.py", line 4, in <module>
from schemas.supplier_schema import Supplier, SupplierCreate
File "/home/phat/projects/crdle2-api/./schemas/supplier_schema.py", line 4, in <module>
from schemas.category_schema import Category
File "/home/phat/projects/crdle2-api/./schemas/category_schema.py", line 4, in <module>
from schemas.supplier_schema import Supplier
ImportError: cannot import name 'Supplier' from partially initialized module 'schemas.supplier_schema' (most likely due to a circular import) (/home/phat/projects/crdle2-api/./schemas/supplier_schema.py)
What am I doing wrong? How can I fix this?
Solution
So, I solved the issue by using annotations from __future__ import annotations and using pydantic’s update_forward_refs
supplier_schema.py
from __future__ import annotations
from pydantic import BaseModel
from typing import Optional, List
from datetime import datetime
# import schemas
class SupplierBase(BaseModel):
company_email: Optional[str] = None
logo: Optional[str] = None
state_province: str = None
city_area: Optional[str] = None
location: Optional[str] = None
company_phone: str = None
fax: Optional[str] = None
tagline: Optional[str] = None
company_bio: Optional[str] = None
postal_code: Optional[str] = None
year_established: str = None
employees_count: Optional[str] = None
certificates: Optional[List[dict]] = []
cover_image: Optional[str] = None
gallery: Optional[List[dict]] = None
license: Optional[str] = None
website: Optional[str] = None
whatsapp_number: Optional[str] = None
facebook_url: Optional[str] = None
twitter_url: Optional[str] = None
linkedin_url: Optional[str] = None
pinterest_url: Optional[str] = None
instagram_url: Optional[str] = None
youtube_url: Optional[str] = None
annual_revenue: Optional[str] = None
payment_methods: Optional[List[dict]] = None
challenges: Optional[List[str]] = []
status: str = None
user_id: int
class Config:
orm_mode = True
class SupplierCreate(SupplierBase):
pass
class Supplier(SupplierBase):
id: int
categories: Optional[List[Category]] = []
created_at: datetime
updated_at: datetime
from .category_schema import Category # nopep8
Category.update_forward_refs()
category_schema.py
from __future__ import annotations
from typing import List
from pydantic import BaseModel
from datetime import datetime
class CategoryBase(BaseModel):
label: str
class Config:
orm_mode = True
class CategoryCreate(CategoryBase):
pass
class Category(CategoryBase):
id: int
created_at: datetime
updated_at: datetime
suppliers: List[Supplier]
from .supplier_schema import Supplier # nopep8
Category.update_forward_refs()
class CategorySkeleton(CategoryBase):
pass
class CategoryPatch(CategoryBase):
pass
Answered By – phatnael
This Answer collected from stackoverflow, is licensed under cc by-sa 2.5 , cc by-sa 3.0 and cc by-sa 4.0