[英]Python 2.7, defining a base class with attributes, id with init constructor
I am trying to define a generic base class Geometry
, with a unique id for each object starting at 0. I am using init as the method. 我试图定义一个通用基类
Geometry
,每个对象的唯一ID从0开始。我使用init作为方法。
I am trying to create a generic base class named Geometry
that I will use to organize geometry objects like point or polygon and containing an id
attribute starting at 0. I know all of the objects should have a unique ID. 我正在尝试创建一个名为
Geometry
的通用基类,该类将用于组织诸如点或多边形之类的几何对象,并包含从0开始的id
属性。我知道所有对象都应具有唯一的ID。 I'm using the constructor ( __init__
) when creating a new Geometry object (integer). 创建新的Geometry对象(整数)时,我正在使用构造函数(
__init__
)。 And would like for the base class to automatically assign the ID of the Geometry object. 并希望为基类自动分配Geometry对象的ID。
Current code: 当前代码:
class Geometry(object):
def__init__(self,id):
self.id = id
I think I am on the right path but I am not positive. 我认为我走了正确的道路,但我并不乐观。 Should I have
id = 0
above def__init__(self,id)
? 我是否应该在
def__init__(self,id)
之上def__init__(self,id)
id = 0
?
Any guidance will be appreciated. 任何指导将不胜感激。
If the first line of your class is id = 0
then it becomes a class attribute and is shared by all instances of Geometry
and all of its children. 如果您的类的第一行
id = 0
则它将成为类属性,并且由Geometry
的所有实例及其所有子代共享。
Here is an example of using a class scoped variable: 这是使用类范围变量的示例:
#!/usr/bin/env python2
class Geometry(object):
# ident is a class scoped variable, better known as Geometry.ident
ident = 0
def __init__(self):
self.ident = Geometry.ident
Geometry.ident += 1
class Circle(Geometry):
def __init__(self, radius):
Geometry.__init__(self)
self.radius = radius
def __str__(self):
return '<Circle ident={}, {}>'.format(self.ident, self.radius)
class Equilateral(Geometry):
def __init__(self, sides, length):
# super is another way to call Geometry.__init__() without
# needing the name of the parent class
super(Equilateral, self).__init__()
self.sides = sides
self.length = length
def __str__(self):
return '<Equilateral ident={}, {}, {}>'.format(self.ident,
self.sides, self.length)
# test that ident gets incremented between calls to Geometry.__init__()
c = Circle(12)
e = Equilateral(3, 8)
f = Circle(11)
print c
assert c.ident == 0
print e
assert e.ident == 1
print f
assert f.ident == 2
Something feels wrong about this, though I've not put my finger on it. 尽管我还没全力以赴,但还是有一点不对劲。
class Geometry(object):
def __init__(self,id=0):
self.id = id
__init__
in python is invoked when you create an instance of that class 创建该类的实例时,将在python中调用
__init__
circle = Geometry(1)
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