Python 更改类变量
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/15790493/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
Python changing class variables
提问by user2154113
Okay, I'll try and be extremely clear this time.
好的，这次我会尽量说清楚。
class Yes:
def __init__(self):
self.a=1
def yes(self):
if self.a==1:
print "Yes"
else:
print "No, but yes"
class No(Yes):
def no(self):
if self.a==1:
print "No"
else:
print "Yes, but no"
self.a-=1 #Note this line
Now, while running:
现在，在运行时：
Yes().yes()
No().no()
Yes().yes()
No().no()
I want it to print out:
我希望它打印出来：
Yes
No
No, but yes
Yes, but no
It gives me:
它给了我：
Yes
No
Yes
No
Now, I know the reason why is because I'm only changing the value of Self.a in the No class(Remember that line?). I want to know if there is anyway to change it in the Yes class while still in the No class (like if there was something that I could plug in in place of the self.a-=1 that would work).
现在，我知道原因是因为我只是在 No 类中更改 Self.a 的值（还记得那行吗？）。我想知道是否有任何方式在 Yes 类中更改它，而仍然在 No 类中（就像我可以插入一些东西来代替 self.a-=1 可以工作）。
采纳答案by Francis Avila
I'm not sure what possible use you have for this, but...
我不确定你有什么可能的用途，但是......
You want to manipulate a classvariable, but you keep addressing instance variables. If you want a class variable, use a class variable!
你想操作一个类变量，但你一直在处理实例变量。如果你想要一个类变量，使用一个类变量！
class Yes:
a = 1 # initialize class var.
def __init__(self):
self.a = 1 # point of this is what?
def yes(self):
if Yes.a==1: # check class var
print "Yes"
else:
print "No, but yes"
class No(Yes):
def no(self):
if Yes.a==1: # check class var
print "No"
else:
print "Yes, but no"
Yes.a-=1 # alter class var
回答by Jesse Vogt
It appears what you want to use is a static variable rather than an instance variable. A static variable is shared between all the instances of the class.
看来您要使用的是静态变量而不是实例变量。静态变量在类的所有实例之间共享。
class Yes:
a = 1
def __init__(self):
pass
def yes(self):
if Yes.a==1:
print "Yes"
else:
print "No, but yes"
class No(Yes):
def no(self):
if Yes.a==1:
print "No"
else:
print "Yes, but no"
Yes.a-=1 #Note this line
Yes().yes()
No().no()
Yes().yes()
No().no()
Will output:
将输出：
Yes
No
No, but yes
Yes, but no
