query_first_or_default
query_first_or_default can execute a query and serialize the first result, or return a default value if the result
set contains no records.
Parameters🔗
| name | type | description | optional | default |
|---|---|---|---|---|
| sql | str |
the sql query str to execute |  |
|
| default | Any |
any object to return if the result set is empty | |
|
| 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 datetime
from dataclasses import dataclass
from pydapper import connect
@dataclass
class Task:
id: int
description: str
due_date: datetime.date
owner_id: int
sentinel = object()
with connect() as commands:
task = commands.query_first_or_default("select * from task where id = -1", model=Task, default=sentinel)
if task is sentinel:
print("No results found!")
# No results found!