cpulimiter 1.0.9

A Python library for Windows to programmatically limit the CPU usage of running processes

cpulimiter 🌡️

A simple, lightweight Python library for Windows to limit the CPU usage of any running process. Reduce CPU load, save power, and prevent overheating.

🤔 Why cpulimiter?

Have you ever had a program like Google Chrome, a game, or a background task consume 100% of your CPU, making your system unresponsive and your fans spin like a jet engine?

cpulimiter solves this by throttling the application, allowing you to specify exactly how much CPU it can use. This is perfect for:

• 🎮 Capping the CPU usage of games to prevent overheating.
• 🌐 Limiting resource-hungry browsers like Chrome or Edge when running multiple tabs.
• 💼 Running heavy data processing or video encoding tasks in the background without slowing down your machine.
• 🔋 Saving battery life on laptops by reducing the power consumption of demanding applications.
• 🤫 Quieting down noisy CPU fans.

✨ Features

• 🎯 Limit CPU Usage: Throttle process CPU usage to a specific percentage.
• 🔍 Flexible Targeting: Target processes by Process ID (PID), executable name ("chrome.exe"), or even window title.
• 🤝 Multi-Process Management: Control and limit multiple processes at the same time.
• 🛠️ Process Discovery: Includes utility functions to find running applications and the active foreground window.
• 🕊️ Lightweight: Has a minimal performance footprint and no external dependencies.

📦 Installation

pip install cpulimiter

📖 Quick Start

The following example limits all chrome.exe processes to just 5% of a single CPU core's power (a 95% limit).

from cpulimiter import CpuLimiter
import time

# 1. Find all "chrome.exe" processes and limit them to 5% CPU.
# The limit is a percentage (0-100). 95 means "limit by 95%", so it can only use 5%.
limiter = CpuLimiter({"chrome.exe": 95})

# 2. The limiter is now running in the background.
# Let's keep it running for 15 seconds to see the effect.
print("Limiting Chrome's CPU usage for 15 seconds...")
time.sleep(15)

# 3. To stop limiting, simply call the shutdown() method.
limiter.shutdown()
print("CPU limit removed. Chrome is back to normal.")

You can check your Task Manager to see the effect in real-time!

⚙️ How It Works

cpulimiter works by rapidly suspending and resuming the threads of a target process. For example, to achieve a 50% CPU limit, the library suspends the process for 10 milliseconds and then resumes it for 10 milliseconds, effectively cutting its CPU time in half. This cycle is managed by a lightweight, high-precision background thread.

📚 Examples

Check out the examples/ folder for more advanced use cases:

• basic_usage.py - A simple, manual introduction to the library's methods.
• simple_limit.py - Manually limit a list of specific applications.
• cpu_saver.py - An automatic CPU saver that throttles all applications that are not in the foreground.
• advanced_interactive.py - An interactive command-line tool for real-time process management.
• modify_limit_example.py - Demonstrates how to change the CPU limit of a process that is already being managed.

API Reference

CpuLimiter Class

The primary class for managing process limits.

limiter.add(pid, process_name, window_title_contains, limit_percentage)

Adds a process to the limiter's management list. If the process is already managed, this will update its CPU limit percentage.

• pid (int): The Process ID.
• process_name (str): The executable name (e.g., "chrome.exe").
• window_title_contains (str): A substring to match in a window title.
• limit_percentage (int): The percentage by which to limit the CPU (e.g., 95 means the process can use up to 5% of a core).

limiter.modify_limit(pid, process_name, window_title_contains, new_limit_percentage)

Modifies the CPU limit for a process that is already being actively limited.

• pid, process_name, window_title_contains: Identifiers for the process to modify.
• new_limit_percentage (int): The new limit to apply.

limiter.start(pid, process_name, window_title_contains)

Starts the CPU limit on a specific, previously added process.

limiter.stop(pid, process_name, window_title_contains)

Stops the CPU limit on a specific process.

limiter.start_all()

Starts the CPU limit on all managed processes.

limiter.stop_all()

Stops the CPU limit on all managed processes.

Utility Functions

get_active_window_info()

Returns a dictionary containing the pid, name, and title of the foreground window.

get_active_app_pids()

Returns a dictionary of all processes with visible windows, mapping their PIDs to their executable names.

🤝 Contributing

Contributions, issues, and feature requests are welcome! Feel free to check the issues page.

📜 License

This project is licensed under the MIT License - see the LICENSE file for details.