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Python

Python Core

Concurrent

Bytes

How to get the size of a byte

import struct
size = struct.calcsize(b"test")

threading.Thread

  • When you want to use Thread class to do some thread-relating work, you can initialze Thread class by customize arguments and use Thread.start() to let the job start running, and make sure you should override Thread.run() instead of directly invoke

queue.Queue

  • When Queue is initialized, the unfinished_tasks is also set to be 0, it would keep increased when put method is invoked, but it do not decresed when get method is invoked on contrary. The only way to make it decreasing is to invoke task_done from outside

Interpreter

readline bug

according to interpreter document, python support typing [ctrl-p] to retreive history command and other arrow button to do editing,

it all depends on GUN readline library, its a very useful tool to do some just in time test.

but with unknown reason, it just not working at my ubuntu machine, like when I click "up" button,
it outputs the "^[[A" which was suppose to be history command like "exit()"

here is my solution, it may not work for you, its a simple record here.

$ conda/pip uninstall readline

for more details and further resource, you can check out below:
GUN readline python interpreter

Python Third Party

Fastapi

How to return a response with image from an ndarray?

https://stackoverflow.com/questions/71595635/render-numpy-array-in-fastapi/71639658#71639658

Uvicorn

What happend when the uvicorn start a server?

  • When the uvicorn start a server, it first load the config as follow:

    config = Config(app, *args, **kwargs)
server = Server(config=config)

    this loads the app path which is not the truly running instance.

  • then, the uvicorn setup the variable _event_loop_policy of python package asyncio to uvloop.EventLoopPolicy which looks like is a Cython class that designed to speed up the server executions.

    asyncio.set_event_loop_policy(uvloop.EventLoopPolicy())

  • After the asyncio's environment is ready, the uvicorn instantly start all the synchronize services.

    config.load()  # this truely instantiate app class with configs.
await server.startup(sockets=sockets)  # this creates a TCP server which take full use of uvloop