How to parse list of models with Pydantic
Question:
I use Pydantic to model the requests and responses to an API.
I defined a User
class:
from pydantic import BaseModel
class User(BaseModel):
name: str
age: int
My API returns a list of users which I retrieve with requests
and convert into a dict:
users = [{"name": "user1", "age": 15}, {"name": "user2", "age": 28}]
How can I convert this dict to a list of User
instances?
My solution for now is
user_list = []
for user in users:
user_list.append(User(**user))
Answers:
You can try this
from typing import List
from pydantic import BaseModel
class User(BaseModel):
name: str
age: int
class Users(BaseModel):
users: List[User]
users = [{"name": "user1", "age": 15}, {"name": "user2", "age": 28}]
m = Users(users=users)
print(m.dict())
You could consider using a list comprehension along with dict unpacking to the User
constructor
user_list = [
User(**user) for user in users
]
You can use the __root__
Pydantic keyword:
from typing import List
from pydantic import BaseModel
class User(BaseModel):
name: str
age: int
class UserList(BaseModel):
__root__: List[User] # ⯇-- __root__
To build the JSON response:
user1 = {"name": "user1", "age": 15}
user2 = {"name": "user2", "age": 28}
user_list = UserList(__root__=[])
user_list.__root__.append(User(**user1))
user_list.__root__.append(User(**user2))
Your API web framework can jsonify user_list
to be returned as a JSON array (within the response body).
To confirm and expand the previous answer, here is an "official" answer at pydantic-github – All credits to "dmontagu":
The "right" way to do this in pydantic is to make use of "Custom Root
Types". You still need to make use of a container model:
class UserList(BaseModel):
__root__: List[User]
but then the following will work:
UserList.parse_obj([
{'id': '123', 'signup_ts': '2017-06-01 12:22', 'friends': [1, '2', b'3']},
{'id': '456', 'signup_ts': '2017-06-02 12:22', 'friends': ['you']},
])
(and will put the values inside the root property).
Unfortunately, I think there is not good serialization support for
this yet, so I think when you go to return the results, if you want to
return just a list you’ll still need to return UserList.root.
I don’t think there is currently a unified interface that gets you a
serialized/unstructured version of the model that respects the
root_model, but if this is what you are looking for, it could be worth building.
This is now possible using parse_obj_as
.
from pydantic import parse_obj_as
users = [
{"name": "user1", "age": 15},
{"name": "user2", "age": 28}
]
m = parse_obj_as(List[User], users)
I have another idea to simple this code if pydantic version below 1.2 that doesn’t support parse_obj_as method.
user_list = []
for user in users:
user_list.append(User(**user))
simple way
user_list = [User(**user) for user in users]
I just set in my models.py
list of dict like this:
from django.db import models
from pydantic import BaseModel
class CustomList(BaseModel):
data: list[dict]
I use Pydantic to model the requests and responses to an API.
I defined a User
class:
from pydantic import BaseModel
class User(BaseModel):
name: str
age: int
My API returns a list of users which I retrieve with requests
and convert into a dict:
users = [{"name": "user1", "age": 15}, {"name": "user2", "age": 28}]
How can I convert this dict to a list of User
instances?
My solution for now is
user_list = []
for user in users:
user_list.append(User(**user))
You can try this
from typing import List
from pydantic import BaseModel
class User(BaseModel):
name: str
age: int
class Users(BaseModel):
users: List[User]
users = [{"name": "user1", "age": 15}, {"name": "user2", "age": 28}]
m = Users(users=users)
print(m.dict())
You could consider using a list comprehension along with dict unpacking to the User
constructor
user_list = [
User(**user) for user in users
]
You can use the __root__
Pydantic keyword:
from typing import List
from pydantic import BaseModel
class User(BaseModel):
name: str
age: int
class UserList(BaseModel):
__root__: List[User] # ⯇-- __root__
To build the JSON response:
user1 = {"name": "user1", "age": 15}
user2 = {"name": "user2", "age": 28}
user_list = UserList(__root__=[])
user_list.__root__.append(User(**user1))
user_list.__root__.append(User(**user2))
Your API web framework can jsonify user_list
to be returned as a JSON array (within the response body).
To confirm and expand the previous answer, here is an "official" answer at pydantic-github – All credits to "dmontagu":
The "right" way to do this in pydantic is to make use of "Custom Root
Types". You still need to make use of a container model:
class UserList(BaseModel):
__root__: List[User]
but then the following will work:
UserList.parse_obj([
{'id': '123', 'signup_ts': '2017-06-01 12:22', 'friends': [1, '2', b'3']},
{'id': '456', 'signup_ts': '2017-06-02 12:22', 'friends': ['you']},
])
(and will put the values inside the root property).
Unfortunately, I think there is not good serialization support for
this yet, so I think when you go to return the results, if you want to
return just a list you’ll still need to return UserList.root.I don’t think there is currently a unified interface that gets you a
serialized/unstructured version of the model that respects the
root_model, but if this is what you are looking for, it could be worth building.
This is now possible using parse_obj_as
.
from pydantic import parse_obj_as
users = [
{"name": "user1", "age": 15},
{"name": "user2", "age": 28}
]
m = parse_obj_as(List[User], users)
I have another idea to simple this code if pydantic version below 1.2 that doesn’t support parse_obj_as method.
user_list = []
for user in users:
user_list.append(User(**user))
simple way
user_list = [User(**user) for user in users]
I just set in my models.py
list of dict like this:
from django.db import models
from pydantic import BaseModel
class CustomList(BaseModel):
data: list[dict]