PyMultiFunc – Your Assistant for Function Overloading

Method and Function Overloading in Python

How Does It Work? (🇺🇸)

PyMultiFunc overloading works similarly to languages that provide overloading "out of the box".

Let’s look at a basic example:

from py_multi_func.override import overload

@overload()
def foo(a: int):
    print("called func `int`")

@overload()
def foo(a: str):
    print("called func `str`")

foo(5)      # called func `int`
foo("str")  # called func `str`

Inheritance Analysis

Do we need to specify the type as an abstract class? Here’s a simple example with cars:

from py_multi_func.override import overload
from abc import ABC


class Car(ABC):
    """Somethink code for car class..."""
    ...


class BMW(Car):
    """I think it could be I8"""
    ...


class Tesla(Car):
    """Tesla Roa..., no Tesla X, yes, of course X"""
    ...


class Lada(Car):
    """I don't care which model is going to be here."""
    ...


@overload()
def foo(car: Car):
    print("called with `Car` or children `Car`")


@overload()
def foo(car: BMW):
    print("called with `BMW`")


@overload()
def foo(car: Tesla):
    print("called with `Tesla`")


foo(Lada())     # called with `Car` or children `Car`
foo(BMW())      # called with `BMW`
foo(Tesla())    # called with `Tesla`

Overloading by Number of Arguments

You can also overload your functions based on the number of arguments:

from py_multi_func.override import overload


@overload()
def foo(a: int):
    print("a = int")


@overload()
def foo(a: int, b: int):
    print("a = int, b = int")


foo(5)        # a = int
foo(5, 5)     # a = int, b = int

Overloading with Default Values

Instead of passing an argument directly, you can use the DEFAULT_ARG class to represent a default value.

Warning

To ensure the class and its replacement as a default argument work correctly, you must follow several rules:

1. The constructor of DEFAULT_ARG must be given the type that corresponds to the argument with the default value.
2. DEFAULT_ARG must be positioned exactly where the argument has a default value — for example, you cannot do this:

from py_multi_func.override import overload
from py_multi_func.defaults_arg import DEFAULT_ARG


@overload()
def foo(a: str, b: str = "default"):
    print(a, b)


# NoDefaultValueForThisArgError: The argument [a] marked as (DEFAULT_ARG) does not have a default value.
# A good error that tells you where the `DEFAULT_ARG` is passed incorrectly
foo(DEFAULT_ARG(str), "somethink") 

3. An initialized DEFAULT_ARG cannot be passed due to the specifics of how the decorator works. If you need to pass such a value explicitly, use FAKE_DEFAULT_ARG instead — it is identical to DEFAULT_ARG, but it is not replaced with the default value.

from py_multi_func.override import overload
from py_multi_func.defaults_arg import DEFAULT_ARG


@overload()
def foo(a: str, b: str = "default"):
    print(a, b)


foo("shprot", "oli")             # shprot oli
foo("this", DEFAULT_ARG(str))    # this default

Brief Overview of the Project Structure

Note

• [📄(🐍)] override.py - Contains the main logic of the decorato
• [📄(🐍)] exception.py - Contains all exceptions that may occur when working with PyMultiFunc
• [📄(🐍)] config.py - Contains constants and other static arguments for analysis during decorator execution
• [📄(🐍)] defaults_arg.py - Contains classes (DEFAULT_ARG and others) that provide access to overriding arguments with default values
• [📁] tests - Contains tests for the decorator
• └── [📁] unittest - Unittest for decorater