What is threading in Python?

🔹 What is threading in Python?

• Threading means running multiple threads of execution within the same process.
• A thread is the smallest unit of a program that can run independently.

• In Python, threads are often used for tasks like:

  • Handling multiple user requests in a web server.
  • Running background tasks (like sending emails, logging, or processing data).
  • Improving responsiveness (so the program doesn’t “freeze” while waiting for something).

👉 Example:

import threading
import time

def worker(name):
    print(f"{name} started")
    time.sleep(2)
    print(f"{name} finished")

# Create 2 threads
t1 = threading.Thread(target=worker, args=("Thread-1",))
t2 = threading.Thread(target=worker, args=("Thread-2",))

t1.start()
t2.start()

This runs two “workers” at the same time (interleaved).

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🔹 Why use threading in Django?

• Django (and many web servers like Gunicorn or Uvicorn) may serve multiple users at once.
• Each request may be handled by a different thread.
• If you need some data specific to a request/thread (like which website/domain is being used), you can store it in thread-local storage so that it doesn’t get mixed up with another request.

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🔹 What is _thread_local?

_thread_local = threading.local()

• threading.local() creates a thread-local storage object.
• That means each thread can store its own attributes without interfering with other threads.
• _thread_local is just a variable name (the underscore _ is a Python convention meaning “this is private, internal use”).

👉 Example:

import threading

local_data = threading.local()

def worker(name):
    local_data.value = name
    print(f"In {name}, local_data.value = {local_data.value}")

t1 = threading.Thread(target=worker, args=("Thread-1",))
t2 = threading.Thread(target=worker, args=("Thread-2",))

t1.start()
t2.start()

Each thread has its own local_data.value → no conflict.

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✅ Summary in plain words:

• Threading = running multiple requests at once.
• threading.local() = keeps request-specific data separate.
• _thread_local.current_website = acts like a per-request global variable.
• Underscore _ = naming convention meaning “internal use only”.