pycyphal.application.register.backend.static module

class pycyphal.application.register.backend.static.StaticBackend(location: Union[None, str, pathlib.Path] = None)

Bases: pycyphal.application.register.backend.Backend

Register storage backend implementation based on SQLite. Supports either persistent on-disk single-file storage or volatile in-memory storage.

>>> b = StaticBackend("my_register_file.db")
>>> b.persistent    # If a file is specified, the storage is persistent.
True
>>> b.location
'my_register_file.db'
>>> b.close()
>>> b = StaticBackend()
>>> b.persistent    # If no file is specified, the data is kept in-memory.
False
>>> from pycyphal.application.register import Bit
>>> b["foo"] = Value(bit=Bit([True, False, True]))   # Create new register.
>>> b["foo"].mutable
True
>>> list(b["foo"].value.bit.value)
[True, False, True]
>>> b["foo"] = Value(bit=Bit([False, True, True]))  # Set new value.
>>> list(b["foo"].value.bit.value)
[False, True, True]
>>> list(b)
['foo']
>>> del b["foo"]
>>> list(b)
[]

__init__(location: Union[None, str, pathlib.Path] = None)

Parameters

location – Either a path to the database file, or None. If None, the data will be stored in memory.

The database is always initialized with check_same_thread=False to enable delegating its initialization to a thread pool from an async context. This is important for this library because if one needs to initialize a new node from an async function, calling the factories directly may be unacceptable due to their blocking behavior, so one is likely to rely on asyncio.loop.run_in_executor(). The executor will initialize the instance in a worker thread and then hand it over to the main thread, which is perfectly safe, but it would trigger a false error from the SQLite engine complaining about the possibility of concurrency-related bugs.

property location: str

property persistent: bool

close() → None

index(index: int) → Optional[str]

setdefault(key: str, default: Optional[Union[pycyphal.application.register.backend.Entry, uavcan.register.Value_1_0.Value_1_0]] = None) → pycyphal.application.register.backend.Entry

__getitem__(key: str) → pycyphal.application.register.backend.Entry

__setitem__(key: str, value: Union[pycyphal.application.register.backend.Entry, uavcan.register.Value_1_0.Value_1_0]) → None

If the register does not exist, it will be implicitly created. If the value is an instance of Value, the mutability flag defaults to the old value or True if none.

__delitem__(key: str) → None

__iter__() → Iterator[str]

__len__() → int