Question

对于可以使用两个不同的单参数构造函数初始化的类，这是正确的做法吗？假设参数可以是字符串或int：

def __init__(self,param):
    if(isinstance(param,basestring)):
        #Initialize using param (string)
    elif(isinstance(param,int)):
        #Initialize using param (int)
    else:
        raise Exception("Invalid param type - must be int or string.")

Answer 1

我认为你可以在python 3.4中使用functools.singledispatch做一些有趣的事情。但事实证明它有点麻烦。

from functools import singledispatch

class A:

    def __init__(self, first_arg, another_arg=None):
        A._init(first_arg, self, another_arg)

    @singledispatch
    def _init(arg0, self, arg1):
        raise TypeError(arg0)

    @_init.register(int)
    def _init_int(arg0, self, arg1):
        print('_init_int', arg0, arg1)
        self.arg = arg0

    @_init.register(str)
    def _init_str(arg0, self, arg1):
        print('_init_str', arg0, arg1)
        self.arg = arg0

A(1)
A('str')
class MyInt(int):
    pass
A(MyInt(3))
A([])

产生

_init_int 1 None
_init_str str None
_init_int 3 None
Traceback (most recent call last):
  File "multi_init.py", line 32, in <module>
    A([])
  File "multi_init.py", line 8, in __init__
    A._init(first_arg, self, another_arg)
  File "/usr/lib/python3.4/functools.py", line 707, in wrapper
    return dispatch(args[0].__class__)(*args, **kw)
  File "multi_init.py", line 12, in _init
    raise TypeError(arg0)
TypeError: []

具有相同参数数量的多个构造函数

1 个答案: