Python 在实例方法中更新类变量
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Updating Class variable within a instance method
提问by f.rodrigues
class MyClass:
var1 = 1
def update(value):
MyClass.var1 += value
def __init__(self,value):
self.value = value
MyClass.update(value)
a = MyClass(1)
I'm trying to update a class variable(var1) within a method(_init_) but I gives me:
我正在尝试在方法（_ init_）中更新类变量（var1），但我给了我：
TypeError: unbound method update() must be called with MyClass instance as first argument (got int instance instead)
I'm doing this because I want easy access to all variables in a class by calling print MyClass.var1
我这样做是因为我希望通过调用 print MyClass.var1 轻松访问类中的所有变量
采纳答案by jonrsharpe
You are confusing classesand instances.
你混淆了类和实例。
class MyClass(object):
pass
a = MyClass()
MyClassis a class, ais an instance of that class. Your error here is that updateis an instance method. To call it from __init__, use either:
MyClass是一个类，a是该类的一个实例。您的错误是这update是一个实例方法。要从 调用它__init__，请使用：
self.update(value)
or
或者
MyClass.update(self, value)
Alternatively, make updatea class method:
或者，创建update一个类方法：
@classmethod
def update(cls, value):
cls.var1 += value
回答by damienfrancois
You need to use the @classmethoddecorator:
您需要使用@classmethod装饰器：
$ cat t.py
class MyClass:
var1 = 1
@classmethod
def update(cls, value):
cls.var1 += value
def __init__(self,value):
self.value = value
self.update(value)
a = MyClass(1)
print MyClass.var1
$ python t.py
2
