函数重载主要是为了解决两个问题。
- 可变参数类型。
- 可变参数个数。
另外，一个基本的设计原则是，仅仅当两个函数除了参数类型和参数个数不同以外，其功能是完全相同的，此时才使用函数重载，如果两个函数的功能其实不同，那么不应当使用重载，而应当使用一个名字不同的函数。
好吧，那么对于情况 1 ，函数功能相同，但是参数类型不同，python 如何处理？答案是根本不需要处理，因为 python 可以接受任何类型的参数，如果函数的功能相同，那么不同的参数类型在 python 中很可能是相同的代码，没有必要做成两个不同函数。
那么对于情况 2 ，函数功能相同，但参数个数不同，python 如何处理？大家知道，答案就是缺省参数。对那些缺少的参数设定为缺省参数即可解决问题。因为你假设函数功能相同，那么那些缺少的参数终归是需要用的。
好了，鉴于情况 1 跟 情况 2 都有了解决方案，python 自然就不需要函数重载了。
I‘m learning Python (3.x) from a Java background.
I have a python program where I create a personObject and add it to a list.
p = Person("John")
list.addPerson(p)
But for flexibility I also want to be able to declare it directly in the addPerson method, like so:
list.addPerson("John")
The addPerson method will be able to differentiate whether or not I‘m sending a Person-object or a String.
In Java I would create two separate methods, like this:
void addPerson(Person p) {
//Add person to list
}
void addPerson(String personName) {
//Create Person object
//Add person to list
}
I‘m not able to find out how to do this in Python. I know of a type() function, which I could use to check whether or not the parameter is a String or an Object. However, that seems messy to me. Is there another way of doing it?
EDIT:
I guess the alternative workaround would be something like this(python):
def addPerson(self, person):
//check if person is string
//Create person object
//Check that person is a Person instance
//Do nothing
//Add person to list
But it seems messy compared to the overloading solution in Java.
Using the reference pointed by @Kevin you can do something like:
from multimethod import multimethod
class Person(object):
def __init__(self, myname):
self.name = myname
def __str__(self):
return self.name
def __repr__(self):
return self.__str__()
@multimethod(list, object)
def addPerson(l, p):
l = l +[p]
return l
@multimethod(list, str)
def addPerson(l, name):
p = Person(name)
l = l +[p]
return l
alist = []
alist = addPerson(alist, Person("foo"))
alist = addPerson(alist, "bar")
print(alist)
The result will be:
$ python test.py [foo, bar]
(you need to install multimethod first)
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