query_single_async
query_single_async can execute a query and serialize the first result. It throws an exception if there is not exactly one
record in the result set.
Parameters🔗
| name | type | description | optional | default |
|---|---|---|---|---|
| sql | str |
the sql query str to execute |  |
|
| param | ParamType |
params to substitute in the query |  |
None |
| model | Any |
the callable to serialize the model; callable must be able to accept column names as kwargs. | |
dict |
First, Single and Default🔗
Be careful to use the right method. first and single methods are very different.
| method | no item | one item | many items |
|---|---|---|---|
first |
NoResultException |
item | first item |
single |
NoResultException |
item | MoreThanOneResultException |
first_or_default |
default | item | first item |
single_or_default |
default | item | MoreThanOneResultException |
Example🔗
Execute a query and map the first result to a dataclass.
import asyncio
import datetime
from dataclasses import dataclass
from pydapper import connect_async
@dataclass
class Task:
id: int
description: str
due_date: datetime.date
owner_id: int
async def main():
async with connect_async() as commands:
task = await commands.query_single_async("select * from task where id = 1", model=Task)
print(task)
# Task(id=1, description='Set up a test database', due_date=datetime.date(2021, 12, 31), owner_id=1)
asyncio.run(main())