Python：类实例可以计算为任何类型吗？_Python_Class_Tuples

Python：类实例可以计算为任何类型吗？

python class

Python：类实例可以计算为任何类型吗？,python,class,tuples,Python,Class,Tuples,类可以通过其_str__方法充当字符串，也可以通过其_call__方法充当函数。它可以充当列表或元组吗 class A (object): def __???__ (self): return (1, 2, 3) >>> a = A() >>> a * 3 (1, 2, 3, 1, 2, 3, 1, 2, 3) 编辑… 这里有一个更好的例子来帮助澄清上述问题 class Vector (object): def __init

类可以通过其_str__方法充当字符串，也可以通过其_call__方法充当函数。它可以充当列表或元组吗

class A (object):
    def __???__ (self):
        return (1, 2, 3)

>>> a = A()
>>> a * 3
(1, 2, 3, 1, 2, 3, 1, 2, 3)

编辑…

这里有一个更好的例子来帮助澄清上述问题

class Vector (object):
    def __init__ (self):
        self.vec = (1,2,3)
    def __???__ (self):
        # something like __repr__; non-string
        return self.vec

class Widget (object):
    def __init__ (self):
        self.vector = Vector()

>>> w = Widget()
>>> w.vector
(1, 2, 3) # not a string representation (at least, before being repr'd here)

基本上，我想要像_repr_uu这样的东西，它不返回字符串，但在我简单地调用指向向量实例的名称时返回元组（或列表），但我不想失去实例中的其他功能，比如访问其他属性和方法。我也不想使用

w.vector.vec

来获取数据。我希望vector的行为类似于w的元组属性，同时仍然能够执行类似于

w.vector.which（）

，或重写uuu mul\uu的操作，以便通过

w.vector*5

缩放向量。可能吗？

调用str时，该类不充当字符串。它创建并返回一个新的字符串对象。基本上，当您在对象上调用

str（something）

时，实际情况如下：

a = str(someObject)

a = someObject.__str__()

因此，

str

函数基本上可以被认为是这样做的：

def str(variable):
    return variable.__str__()

调用

list（）

、

tuple（）

、

set（）

等时也是如此。如果我认为你的问题是正确的：

tuple（）

、

list（）

和

set（）

都调用类的

\uuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuu
class MyClass(object):
    ...
    def __iter__(self):
        ...
        return myIterable

调用str时，该类不充当字符串。它创建并返回一个新的字符串对象。基本上，当您在对象上调用str（something）
时，实际情况如下：
a = str(someObject)

a = someObject.__str__()

因此，str
函数基本上可以被认为是这样做的：
def str(variable):
    return variable.__str__()

调用list（）
、tuple（）
、set（）
等时也是如此。如果我认为你的问题是正确的：
tuple（）
、list（）
和set（）
都调用类的\uuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuu
class MyClass(object):
    ...
    def __iter__(self):
        ...
        return myIterable

对于示例中的特定行为（A*3
给出了A
中数据的三个串联副本），您希望实现\uuuu mul\uu（）
运算符
例如，这些是等效的：
>>> a = [1,2,3]
>>> a*3
[1, 2, 3, 1, 2, 3, 1, 2, 3]
>>> a.__mul__(3)
[1, 2, 3, 1, 2, 3, 1, 2, 3]
>>> 

更一般地说，如果您想要实现一个序列类型，您必须实现所有的。你必须定义-

A[3]
是什么意思（\uuu getitem\uuuuuuuuuuuuuuuuuuuuuuuu（）
，\uuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuu

什么是A[1:10]
的意思（\uu getslice\uuu（）
）
A:
中项目的表示什么（\uuu iter\uuu（））

等等
以下是list
s上定义的方法的完整列表：
>>> pprint.pprint(dict(list.__dict__))
{'__add__': <slot wrapper '__add__' of 'list' objects>,
 '__contains__': <slot wrapper '__contains__' of 'list' objects>,
 '__delitem__': <slot wrapper '__delitem__' of 'list' objects>,
 '__delslice__': <slot wrapper '__delslice__' of 'list' objects>,
 '__doc__': "list() -> new empty list\nlist(iterable) -> new list initialized from iterable's items",
 '__eq__': <slot wrapper '__eq__' of 'list' objects>,
 '__ge__': <slot wrapper '__ge__' of 'list' objects>,
 '__getattribute__': <slot wrapper '__getattribute__' of 'list' objects>,
 '__getitem__': <method '__getitem__' of 'list' objects>,
 '__getslice__': <slot wrapper '__getslice__' of 'list' objects>,
 '__gt__': <slot wrapper '__gt__' of 'list' objects>,
 '__hash__': None,
 '__iadd__': <slot wrapper '__iadd__' of 'list' objects>,
 '__imul__': <slot wrapper '__imul__' of 'list' objects>,
 '__init__': <slot wrapper '__init__' of 'list' objects>,
 '__iter__': <slot wrapper '__iter__' of 'list' objects>,
 '__le__': <slot wrapper '__le__' of 'list' objects>,
 '__len__': <slot wrapper '__len__' of 'list' objects>,
 '__lt__': <slot wrapper '__lt__' of 'list' objects>,
 '__mul__': <slot wrapper '__mul__' of 'list' objects>,
 '__ne__': <slot wrapper '__ne__' of 'list' objects>,
 '__new__': <built-in method __new__ of type object at 0x1E1DACA8>,
 '__repr__': <slot wrapper '__repr__' of 'list' objects>,
 '__reversed__': <method '__reversed__' of 'list' objects>,
 '__rmul__': <slot wrapper '__rmul__' of 'list' objects>,
 '__setitem__': <slot wrapper '__setitem__' of 'list' objects>,
 '__setslice__': <slot wrapper '__setslice__' of 'list' objects>,
 '__sizeof__': <method '__sizeof__' of 'list' objects>,
 'append': <method 'append' of 'list' objects>,
 'count': <method 'count' of 'list' objects>,
 'extend': <method 'extend' of 'list' objects>,
 'index': <method 'index' of 'list' objects>,
 'insert': <method 'insert' of 'list' objects>,
 'pop': <method 'pop' of 'list' objects>,
 'remove': <method 'remove' of 'list' objects>,
 'reverse': <method 'reverse' of 'list' objects>,
 'sort': <method 'sort' of 'list' objects>}

>>pprint.pprint（dict（list.\uu dict）
{“添加”：，
“\uuuu包含”：，
“uuu delitem”：，
“\uuu delslice\uuuu”：，
“\uuuu doc\uuuuuu”：“列表（）->新空列表\n列表（iterable）->从iterable的项初始化的新列表”，
“uuu eq”：，
""格":,，
“\uuuu getattribute\uuuuuu”：，
“\uuu getitem\uuuu”：，
“\uuu getslice\uuuu”：，
“\uuugt\uuuuuu”：，
“\uuuu散列”：无，
"iadd":,，
“伊穆尔”：，
“\uuuu init\uuuuuuu”：，
“\uuuuu iter\uuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuu，
‘乐’，
“\uuuu len\uuuuuuu”：，
“————————”，
“uuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuu，
“\uuu ne\uuuuu”：，
"新":,，
“报告”：，
“\uuuu反向”：，
""rmul":,，
“\uuuu setitem\uuuuuuuuu”：，
“\uuuu设置许可证”：，
“\uuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuu，
“追加”：，
“计数”：，
“扩展”：，
“索引”：，
“插入”：，
“流行音乐”：，
“删除”：，
“反向”：，
'排序'：}
对于示例中的特定行为（A*3
给出了A
中数据的三个串联副本），您希望实现\u mul\u（）
运算符
例如，这些是等效的：
>>> a = [1,2,3]
>>> a*3
[1, 2, 3, 1, 2, 3, 1, 2, 3]
>>> a.__mul__(3)
[1, 2, 3, 1, 2, 3, 1, 2, 3]
>>> 

更一般地说，如果您想要实现一个序列类型，您必须实现所有的。你必须定义-

A[3]
是什么意思（\uuu getitem\uuuuuuuuuuuuuuuuuuuuuuuu（）
，\uuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuu

什么是A[1:10]
的意思（\uu getslice\uuu（）
）
A:
中项目的表示什么（\uuu iter\uuu（））

等等
以下是list
s上定义的方法的完整列表：
>>> pprint.pprint(dict(list.__dict__))
{'__add__': <slot wrapper '__add__' of 'list' objects>,
 '__contains__': <slot wrapper '__contains__' of 'list' objects>,
 '__delitem__': <slot wrapper '__delitem__' of 'list' objects>,
 '__delslice__': <slot wrapper '__delslice__' of 'list' objects>,
 '__doc__': "list() -> new empty list\nlist(iterable) -> new list initialized from iterable's items",
 '__eq__': <slot wrapper '__eq__' of 'list' objects>,
 '__ge__': <slot wrapper '__ge__' of 'list' objects>,
 '__getattribute__': <slot wrapper '__getattribute__' of 'list' objects>,
 '__getitem__': <method '__getitem__' of 'list' objects>,
 '__getslice__': <slot wrapper '__getslice__' of 'list' objects>,
 '__gt__': <slot wrapper '__gt__' of 'list' objects>,
 '__hash__': None,
 '__iadd__': <slot wrapper '__iadd__' of 'list' objects>,
 '__imul__': <slot wrapper '__imul__' of 'list' objects>,
 '__init__': <slot wrapper '__init__' of 'list' objects>,
 '__iter__': <slot wrapper '__iter__' of 'list' objects>,
 '__le__': <slot wrapper '__le__' of 'list' objects>,
 '__len__': <slot wrapper '__len__' of 'list' objects>,
 '__lt__': <slot wrapper '__lt__' of 'list' objects>,
 '__mul__': <slot wrapper '__mul__' of 'list' objects>,
 '__ne__': <slot wrapper '__ne__' of 'list' objects>,
 '__new__': <built-in method __new__ of type object at 0x1E1DACA8>,
 '__repr__': <slot wrapper '__repr__' of 'list' objects>,
 '__reversed__': <method '__reversed__' of 'list' objects>,
 '__rmul__': <slot wrapper '__rmul__' of 'list' objects>,
 '__setitem__': <slot wrapper '__setitem__' of 'list' objects>,
 '__setslice__': <slot wrapper '__setslice__' of 'list' objects>,
 '__sizeof__': <method '__sizeof__' of 'list' objects>,
 'append': <method 'append' of 'list' objects>,
 'count': <method 'count' of 'list' objects>,
 'extend': <method 'extend' of 'list' objects>,
 'index': <method 'index' of 'list' objects>,
 'insert': <method 'insert' of 'list' objects>,
 'pop': <method 'pop' of 'list' objects>,
 'remove': <method 'remove' of 'list' objects>,
 'reverse': <method 'reverse' of 'list' objects>,
 'sort': <method 'sort' of 'list' objects>}

>>pprint.pprint（dict（list.\uu dict）
{“添加”：，
“\uuuu包含”：，
“uuu delitem”：，
“\uuu delslice\uuuu”：，
“\uuuu doc\uuuuuu”：“列表（）->新空列表\n列表（iterable）->从iterable的项初始化的新列表”，
“uuu eq”：，
""格":,，
“\uuuu getattribute\uuuuuu”：，
“\uuu getitem\uuuu”：，
“\uuu getslice\uuuu”：，
“\uuugt\uuuuuu”：，
“\uuuu散列”：无，
"iadd":,，
“伊穆尔”：，
“\uuuu init\uuuuuuu”：，
“\uuuuu iter\uuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuu，
‘乐’，
“\uuuu len\uuuuuuu”：，
“————————”，
“uuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuu，
“\uuu ne\uuuuu”：，
"新":,，
“报告”：，
“\uuuu反向”：，
""rmul":,，
“\uuuu setitem\uuuuuuuuu”：，
“\uuuu设置许可证”：，
“\uuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuu，
“追加”：，
“计数”：，
“扩展”：，
“索引”：，
“插入”：，
“流行音乐”：，
“删除”：，
“反向”：，
'排序'：}
根据您的目标，您可以创建一个从内置类继承的类，如list
或tuple
：
>>> class A(tuple):
...     def speak(self):
...         print "Bark!"
... 
>>> a = A((1,2,3)) # extra parens needed to distinguish single tuple arg from 3 scalar args
>>> a * 3
(1, 2, 3, 1, 2, 3, 1, 2, 3)
>>> a.speak()
Bark!

考虑到您的向量用例，子类化tuple可能很好地解决了这个问题
import math

class Vector(tuple):
    def magnitude(self):
        return math.sqrt( self[0]*self[0]+self[1]*self[1]+self[2]*self[2] )

根据您的目标，您可以创建一个从内置类继承的类，如list
或tuple
：
>>> class A(tuple):
...     def speak(self):
...         print "Bark!"
... 
>>> a = A((1,2,3)) # extra parens needed to distinguish single tuple arg from 3 scalar args
>>> a * 3
(1, 2, 3, 1, 2, 3, 1, 2, 3)
>>> a.speak()
Bark!

考虑到您的向量用例，子类化tuple可能很好地解决了这个问题
import math

class Vector(tuple):
    def magnitude(self):
        return math.sqrt( self[0]*self[0]+self[1]*self[1]+self[2]*self[2] )

调用\uuuu str\uuuu
时，该类不充当字符串，它创建并返回一个新的字符串对象。我真的不明白你在说什么……当你调用\uuuuu str\uuuuu
时，这个类并不充当字符串，它创建并返回一个新的字符串对象。我真的不明白你在说什么……我知道关于_umul_u_uu_u_u_u_u_u_u_u_u_u_u_u_u_u_u_u_u_u_u_u_u。然而，在我的示例中，我只是试图说明它确实返回了一个元组，而不是元组的字符串表示。它只是简单地使用一个类来充当一个类型，同时还保留了其他功能，比如调用我感兴趣的方法。也许我可以把tuple子类化