fastreactpy ⚡

Fast, lightweight reactive state library for Python.

fastreactpy brings React-like reactive state to Python with zero dependencies, minimal overhead, and a clean API.

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🚀 Installation

pip install fastreactpy

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🧠 Core Concepts

Signal

A signal is a reactive container for state.

from fastreactpy import signal

count = signal(0)

• count() → get value
• count(10) → set value and notify subscribers

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Effect

An effect automatically re-runs when the signals it uses change.

from fastreactpy import effect

@effect
def logger():
    print("Count:", count())

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✨ Basic Example

from fastreactpy import signal, effect

count = signal(0)

@effect
def print_count():
    print("Count changed:", count())

count(5)
count(10)

Output:

Count changed: 0
Count changed: 5
Count changed: 10

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📁 Sharing State Between Multiple Files

This is the most common real-world usage.

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store.py (Shared State)

from fastreactpy import signal

count = signal(0)
user = signal("Guest")

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logger.py (Reactions / Effects)

from fastreactpy import effect
from store import count, user

@effect
def log_count():
    print("[logger] Count:", count())

@effect
def log_user():
    print("[logger] User:", user())

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main.py (Mutating State)

import logger  # IMPORTANT: registers effects
from store import count, user

count(1)
user("Malahim")

count(5)
user("Alice")

Output:

[logger] Count: 0
[logger] User: Guest
[logger] Count: 1
[logger] User: Malahim
[logger] Count: 5
[logger] User: Alice

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🧩 Multiple Effects on One Signal

from fastreactpy import effect
from store import count

@effect
def double():
    print("Double:", count() * 2)

@effect
def square():
    print("Square:", count() ** 2)

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⚡ Why fastreactpy?

• Zero dependencies
• Extremely lightweight
• React-style mental model
• Automatic dependency tracking
• Works across files
• Ideal for CLIs, tools, and services

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⚠️ Best Practices

• Keep shared signals in a single module (e.g. store.py)
• Always import modules that define effects
• Avoid heavy logic inside effects
• Use effects for side-effects only

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🌐 Contact

Website: https://malahim.dev

Phone: +92 328 4671797

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📄 License

MIT License © 2025 Malahim Haseeb