smartswitch 0.2.0

Intelligent rule-based function dispatch for Python

SmartSwitch

Intelligent rule-based function dispatch for Python

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📚 Part of the genro-libs family General-purpose Python developer tools

Replace messy if-elif chains and duplicated logic with clean, maintainable function registries.

Installation

pip install smartswitch

The Problem-Solution Approach

SmartSwitch helps you organize code that needs to handle different cases. Let's see how, step by step.

1. Function Registry Pattern

Problem: You have several operations and want to call them by name.

Traditional approach - Dictionary of functions:

# Hard to maintain, easy to make mistakes
operations = {
    'save': save_data,
    'load': load_data,
    'delete': delete_data
}

# Calling
op = operations.get(action)
if op:
    op(data)

With SmartSwitch - Clean registration:

from smartswitch import Switcher

ops = Switcher()

@ops
def save_data(data):
    # Save logic
    pass

@ops
def load_data(data):
    # Load logic
    pass

@ops
def delete_data(data):
    # Delete logic
    pass

# Call by name
ops('save_data')(data)

2. Custom Action Names

Problem: You want friendly names different from function names.

Traditional approach - Manual mapping:

actions = {
    'reset': destroy_all_data,
    'clear': remove_cache,
    'wipe': erase_history
}

action = actions[command]
action()

With SmartSwitch - Alias registration:

ops = Switcher()

@ops('reset')
def destroy_all_data():
    pass

@ops('clear')
def remove_cache():
    pass

# Call with alias
ops('reset')()

Or use prefix-based auto-naming for convention-driven naming:

# Set a prefix to auto-derive handler names
protocols = Switcher(prefix='protocol_')

@protocols  # Auto-registers as 's3_aws'
def protocol_s3_aws():
    return {"type": "s3", "region": "us-east-1"}

@protocols  # Auto-registers as 'gcs'
def protocol_gcs():
    return {"type": "gcs", "bucket": "data"}

# Call by auto-derived names
protocols('s3_aws')()
protocols('gcs')()

3. Value-Based Dispatch

Problem: Choose handler based on actual data values.

Traditional approach - Long if-elif chains:

def process_user(user_type, reason):
    if user_type == 'to_delete' and reason == 'no_payment':
        # Remove user
        pass
    elif reason == 'no_payment':
        # Send reminder
        pass
    elif user_type == 'to_delete':
        # Archive
        pass
    else:
        # Default
        pass

With SmartSwitch - Declarative rules:

users = Switcher()

@users(valrule=lambda user_type, reason:
       user_type == 'to_delete' and reason == 'no_payment')
def remove_user(user_type, reason):
    # Remove user
    pass

@users(valrule=lambda reason: reason == 'no_payment')
def send_payment_reminder(user_type, reason):
    # Send reminder
    pass

@users(valrule=lambda user_type: user_type == 'to_delete')
def archive_user(user_type, reason):
    # Archive
    pass

@users
def handle_default(user_type, reason):
    # Default
    pass

# Automatic dispatch
users()(user_type='to_delete', reason='no_payment')

Tip: For multi-parameter conditions, you can use compact dict-style lambda:

@users(valrule=lambda kw: kw['user_type'] == 'to_delete' and kw['reason'] == 'no_payment')
def remove_user(user_type, reason):
    pass

4. Type-Based Dispatch

Problem: Handle different data types differently.

Traditional approach - Multiple isinstance checks:

def process(data):
    if isinstance(data, str):
        return data.upper()
    elif isinstance(data, int):
        return data * 2
    elif isinstance(data, list):
        return len(data)
    else:
        return None

With SmartSwitch - Type rules:

processor = Switcher()

@processor(typerule={'data': str})
def process_string(data):
    return data.upper()

@processor(typerule={'data': int})
def process_number(data):
    return data * 2

@processor(typerule={'data': list})
def process_list(data):
    return len(data)

@processor
def process_other(data):
    return None

# Automatic dispatch based on type
processor()(data="hello")  # → HELLO
processor()(data=42)       # → 84

Real-World Examples

API Routing

api = Switcher()

@api(valrule=lambda method, path: method == 'GET' and path == '/users')
def get_users(method, path, data=None):
    return list_all_users()

@api(valrule=lambda method, path: method == 'POST' and path == '/users')
def create_user(method, path, data=None):
    return create_new_user(data)

@api
def not_found(method, path, data=None):
    return {"error": "Not Found", "status": 404}

# Dispatch
response = api()('GET', '/users')

Payment Processing

payments = Switcher()

@payments(typerule={'amount': int | float},
          valrule=lambda method, amount: method == 'crypto' and amount > 1000)
def process_large_crypto(method, amount, details):
    return {"processor": "crypto_large", "fee": amount * 0.01}

@payments(valrule=lambda method, **kw: method == 'credit_card')
def process_card(method, amount, details):
    return {"processor": "credit_card", "fee": amount * 0.03}

@payments
def process_generic(method, amount, details):
    return {"error": "Unsupported payment method"}

When to Use

✅ Good for:

• API handlers and request routers
• Business logic with multiple branches
• Plugin systems and extensible architectures
• State machines and workflow engines
• When you need type + value checks together

⚠️ Consider alternatives for:

• Simple 2-3 case switches → use if/elif
• Pure type dispatch → use functools.singledispatch
• Very high-performance code (< 10μs functions called millions of times)

Key Features

Core Dispatch Mechanisms

• 🔢 Type-based dispatch: Route by argument types (int, str, custom classes, unions)
• 🎯 Value-based dispatch: Match on runtime values with lambda rules
• 🔗 Combined rules: Use type AND value rules together for precise routing

Handler Management

• 📦 Named handler access: Retrieve and call handlers by name
• 🏷️ Custom aliases: Register handlers with user-friendly names
• 🔤 Prefix-based auto-naming: Convention-driven handler registration (NEW in v0.1.0)

Developer Experience

• 🧩 Modular & testable: Each handler is an independent function
• ✨ Clean API: Pythonic decorators with zero boilerplate
• 🚀 Efficient: Optimized with caching (~1-2μs overhead)
• 🛡️ Type-safe: Full type annotation support

Documentation

📚 Full documentation: smartswitch.readthedocs.io

Guides:

• Type Rules - Dispatch based on types
• Value Rules - Dispatch based on runtime values
• Named Handlers - Direct handler access
• Best Practices - Production patterns
• API Reference - Complete API docs

All examples in documentation are tested - They come directly from our test suite with 95% coverage.

Performance

SmartSwitch adds ~1-2 microseconds per dispatch. For real-world functions (API calls, DB queries, business logic), this overhead is negligible:

Function time: 50ms (API call)
Dispatch overhead: 0.002ms
Impact: 0.004% ✅

See Performance Best Practices for more details.

License

MIT

Contributing

Contributions welcome! Please feel free to submit a Pull Request.