我刚刚遇到了重载.py (Python 3的函数重载)，有兴趣的同学可以去看看。

从链接库的README文件:

overloading is a module that provides function dispatching based on the types and number of runtime arguments. When an overloaded function is invoked, the dispatcher compares the supplied arguments to available function signatures and calls the implementation that provides the most accurate match. Features Function validation upon registration and detailed resolution rules guarantee a unique, well-defined outcome at runtime. Implements function resolution caching for great performance. Supports optional parameters (default values) in function signatures. Evaluates both positional and keyword arguments when resolving the best match. Supports fallback functions and execution of shared code. Supports argument polymorphism. Supports classes and inheritance, including classmethods and staticmethods.

你也可以使用pythonlangutil:

from pythonlangutil.overload import Overload, signature

class A:
    @Overload
    @signature()
    def stackoverflow(self):    
        print('first method')
    
    @stackoverflow.overload
    @signature("int")
    def stackoverflow(self, i):
        print('second method', i)

Python在PEP-3124中添加了@overload装饰器，为通过类型检查进行重载提供语法糖——而不仅仅是使用重写。

关于通过PEP-3124中的@overload重载的代码示例

from overloading import overload
from collections import Iterable

def flatten(ob):
    """Flatten an object to its component iterables"""
    yield ob

@overload
def flatten(ob: Iterable):
    for o in ob:
        for ob in flatten(o):
            yield ob

@overload
def flatten(ob: basestring):
    yield ob

由@overload-decorator转换为:

def flatten(ob):
    if isinstance(ob, basestring) or not isinstance(ob, Iterable):
        yield ob
    else:
        for o in ob:
            for ob in flatten(o):
                yield ob

Python不像Java或c++那样支持方法重载。我们可以重载方法，但只能使用最新定义的方法。

# First sum method.
# Takes two argument and print their sum
def sum(a, b):
    s = a + b
    print(s)

# Second sum method
# Takes three argument and print their sum
def sum(a, b, c):
    s = a + b + c
    print(s)

# Uncommenting the below line shows an error
# sum(4, 5)

# This line will call the second sum method
sum(4, 5, 5)

我们需要提供可选参数或*args，以便在调用时提供不同数量的参数。

方法重载

我刚刚遇到了重载.py (Python 3的函数重载)，有兴趣的同学可以去看看。

从链接库的README文件:

overloading is a module that provides function dispatching based on the types and number of runtime arguments. When an overloaded function is invoked, the dispatcher compares the supplied arguments to available function signatures and calls the implementation that provides the most accurate match. Features Function validation upon registration and detailed resolution rules guarantee a unique, well-defined outcome at runtime. Implements function resolution caching for great performance. Supports optional parameters (default values) in function signatures. Evaluates both positional and keyword arguments when resolving the best match. Supports fallback functions and execution of shared code. Supports argument polymorphism. Supports classes and inheritance, including classmethods and staticmethods.

这是方法重载，而不是方法重写。在Python中，你可以在一个函数中完成所有工作:

class A:
    def stackoverflow(self, i='some_default_value'):
        print('only method')

ob=A()
ob.stackoverflow(2)
ob.stackoverflow()

请参阅Python教程的默认实参值部分。请参阅“Least surprise”和可变默认参数，以了解需要避免的常见错误。

有关Python 3.4中添加的单个分派泛型函数的信息，请参阅PEP 443:

>>> from functools import singledispatch
>>> @singledispatch
... def fun(arg, verbose=False):
...     if verbose:
...         print("Let me just say,", end=" ")
...     print(arg)
>>> @fun.register(int)
... def _(arg, verbose=False):
...     if verbose:
...         print("Strength in numbers, eh?", end=" ")
...     print(arg)
...
>>> @fun.register(list)
... def _(arg, verbose=False):
...     if verbose:
...         print("Enumerate this:")
...     for i, elem in enumerate(arg):
...         print(i, elem)