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Python multithreading and multiprocessing

Introduction Reading Time: 10 min

Table of Contents

Description

Multithreading is a programming technique that allows a process to execute multiple threads (smaller units of a process) concurrently. In Python, multithreading is useful for performing tasks like I/O operations, file handling, and network communication simultaneously, thus improving the efficiency and responsiveness of applications. Python uses the threading module to implement multithreading.

Note: Due to Python’s Global Interpreter Lock (GIL), true parallel execution is limited, but multithreading is still useful for I/O-bound tasks.

Prerequisites

  • Understanding of basic Python syntax and functions.
  • Knowledge of processes and threads.
  • Familiarity with time-consuming operations like file access, API calls, or waiting tasks.

Examples

Here's a simple "Hello World" program in Python:

Basic Multithreading in Python:


import threading
import time

def print_numbers():
    for i in range(5):
        print(f"Number: {i}")
        time.sleep(1)

# Creating threads
t1 = threading.Thread(target=print_numbers)
t2 = threading.Thread(target=print_numbers)

# Starting threads
t1.start()
t2.start()

# Waiting for both to finish
t1.join()
t2.join()

print("Finished!")

Real-World Applications

Downloading multiple files simultaneously.

Running background tasks like logging or data collection while main application runs.

Handling multiple client connections in a server.

Building responsive GUI applications that perform background work.

Where topic Can Be Applied

All Web servers: Handling concurrent HTTP requests.

Desktop software: Running background tasks in GUI apps.

Data logging systems: Simultaneous sensor data collection

Chat/messaging apps: Sending and receiving messages without blocking.

Games: Handling user input, physics, and rendering concurrently.

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Interview Questions

What is multithreading and how is it implemented in Python?

What is the Global Interpreter Lock (GIL)?

How does multithreading differ from multiprocessing?

When would you use multithreading instead of multiprocessing?

Can you explain the role of the join() method in threading?