ATdispatcher

ATdispatcher is a flexible Python dispatcher library for creating functions and methods with multiple options (overloads), default arguments, type checking, and automatic handling of instance attributes for methods. It allows a simple API to manage multiple variations of the same function or method.

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Features

• Dispatch multiple function variations under the same name.
• Support for default arguments.
• Support for type hints to select the correct variant.
• Dispatch methods with automatic self and SelfAttr handling.
• Simple API with @dispatcher for functions and @method_dispatcher for methods.
• Easily extendable with multiple registrations using .reg().

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Installation

Currently, ATdispatcher is a standalone module. You can include it in your project directly:

git clone https://github.com/avitwil/ATdispatcher.git
or
pip install ATdispatcher

Or copy ATdispatcher.py into your project directory.

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Usage

Importing

from ATdispatcher import dispatcher, method_dispatcher, SelfAttr

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1. Function Dispatching

@dispatcher
def func(a: int, b: int):
    return a + b

@func.reg()
def _(a: int, b: int, c: int):
    return a + b + c

@func.reg()
def _(a: int, b: int, c: int = 3):
    return a * b * c

print(func(5, 6))        # Output: 11  (matches first variant)
print(func(5, 6, 7))     # Output: 18  (matches second variant)
print(func(5, 6, 3))     # Output: 90  (matches third variant with default)

✅ Notes:

• You can register multiple variants with different signatures using .reg().
• Type hints are used to select the correct variant.
• Default arguments are supported.

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2. Method Dispatching with SelfAttr

SelfAttr allows method defaults to refer to instance attributes automatically.

class MyClass:
    def __init__(self):
        self.mult = 2

    @method_dispatcher
    def method(self, x: int, y: int = SelfAttr("mult")):
        return x * y

obj = MyClass()

print(obj.method(10))     # Output: 20  (y defaults to obj.mult)
print(obj.method(10, 5))  # Output: 50  (y explicitly passed)

✅ Notes:

• SelfAttr("attr_name") automatically fetches self.attr_name as the default.
• Works with multiple method registrations using .reg() as well.

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3. Multiple Method Variants

class MyClass:
    def __init__(self):
        self.mult = 3

    @method_dispatcher
    def calc(self, x: int):
        return x * 2

    @calc.reg()
    def _(self, x: int, y: int = SelfAttr("mult")):
        return x * y

obj = MyClass()

print(obj.calc(5))        # Output: 10  (first variant)
print(obj.calc(5, 4))     # Output: 20  (second variant with y=4)
print(obj.calc(5, 3))     # Output: 15  (second variant, y defaults to obj.mult)

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4. Error Handling

If no matching signature is found:

try:
    func("a", 5)
except TypeError as e:
    print(e)  # Output: No matching function signature found

✅ Type checking ensures invalid calls raise TypeError.

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5. API Reference

Class / Function	Description
dispatcher(func)	Create a function dispatcher.
.reg()	Register a new variant for the same dispatcher.
method_dispatcher(func)	Create a method dispatcher for instance methods.
SelfAttr("attr")	Used for method default arguments that reference self attributes.

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6. Example: Combined Usage

from ATdispatcher import dispatcher, method_dispatcher, SelfAttr

@dispatcher
def add(a: int, b: int):
    return a + b

@add.reg()
def _(a: int, b: int, c: int = 10):
    return a + b + c

class Calc:
    def __init__(self):
        self.multiplier = 5

    @method_dispatcher
    def multiply(self, x: int, y: int = SelfAttr("multiplier")):
        return x * y

calc = Calc()

print(add(1, 2))          # 3
print(add(1, 2, 3))       # 6
print(calc.multiply(4))   # 20
print(calc.multiply(4, 2))# 8

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License

MIT License – free to use, modify, and distribute.