Pure Python asyncio connector to KDB
Project description
aiokdb
Python asyncio connector to KDB. Pure python, so does not depend on the k.h bindings or kdb shared objects, or numpy/pandas. Fully type hinted to comply with PEP-561. No non-core dependancies, and tested on Python 3.9 - 3.11.
Peer review & motivation
qPython is a widely used library for this task and it maps objects to Pandas Dataframes which might be more suitable for the majority of applications.
This library takes a different approach and aims to replicate using the KDB C-library functions, ie. being 100% explicit about KDB types. It was built working from the publically documented Serialization Examples and C API for kdb+ pages. Users might also need to be familiar with k.h.
A simple example:
from aiokdb import khpu
# run ./q -p 12345 &
h = khpu("localhost", 12345, "kdb:pass")
result = h.k("2.0+3.0", None) # None can be used where C expects (K)0
# if the remote returns a Q Exception, this gets raised, unless k(..., raise=False)
assert result.aF() == 5.0
The result object is a K-like Python object (a KObj), having the usual signed integer type available as result.type. Accessors for the primitive types are prefixed with an a and check at runtime that the accessor is appropriate for the stored type (.aI(), .aJ(), .aH(), .aF() etc.). Atoms store their value to a bytes object irrespective of the type, and encode/decode on demand. Atomic values can be set with (.i(3), .j(12), .ss("hello")).
Arrays are implemented with subtypes that use Python's native arrays module for efficient array types. The MutableSequence arrays are returned using the usual array accessor functions .kI(), .kB(), .kS() etc.
Serialisation is handled by b9 which returns a python bytes, and d9 which takes a bytes and returns a K-object.
- Atoms are created by
ka,kb,ku,kg,kh,ki,kj,ke,kf,kc,ks,kt,kd,kz,ktj - Lists with
ktnandknk - Dictionaries with
xdand tables withxt.
Python manages garbage colleciton of our objects, so none of the refcounting primitives exist, ie. k.r and functions r1, r0 and m9, setm have no equivelent.
RPC
Client support using python asyncio is built into the package, and uses prompt_toolkit for line editing:
$ pip install aiokdb prompt_toolkit
$ ./q -p 12345 &
$ python -m aiokdb.cli --host localhost --port 12345
(eval) > ([s:7 6 0Nj]x:3?0Ng;y:2)
s| x y
-|---------------------------------------
7| 409031f3-b19c-6770-ee84-6e9369c98697 2
6| 52cb20d9-f12c-9963-2829-3c64d8d8cb14 2
| cddeceef-9ee9-3847-9172-3e3d7ab39b26 2
(eval) > \\
$
Tests
The unit tests in test/test_rpc.py will use a real KDB binary to test against (over RPC) if you set KDB_PYTEST_SERVICE to a URL of the form kdb://user:password@hostname:port, otherwise that test is skipped and they are self contained.
- Formatting with
ruff check . - Formatting with
black . - imports
isort --check --profile black . - Check type annotations with
mypy --strict . - Run
pytest .in the root directory
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