为什么要记住类属性？ [英] Why class attribute is remembered?

问题描述

这是一个示例python模块：

Here is a sample python module:

# foo.py
class Foo(object):
    a = {}
    def __init__(self):
        print self.a
        self.filla()
    def filla(self):
        for i in range(10):
            self.a[str(i)] = i

然后我在python shell中执行此操作：

then I do this in python shell:

$ python
Python 2.7.2 (default, Jan 13 2012, 17:11:09) 
[GCC 4.2.1 (Apple Inc. build 5666) (dot 3)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> from foo import Foo
>>> f = Foo()
{}
>>> f = Foo()
{'1': 1, '0': 0, '3': 3, '2': 2, '5': 5, '4': 4, '7': 7, '6': 6, '9': 9, '8': 8}

为什么第二次 a 不为空？我错过了一些琐碎的事情吗？

Why the second time a is not empty? Am I missing something trivial.

推荐答案

问题是 a 是不束缚。它是类的属性，而不是对象。您想执行以下操作：

The problem is that a is not bound. It is a property of the class, not the object. You want to do something like this:

# foo.py
class Foo(object):
    def __init__(self):
        self.a = {}
        print self.a
        self.filla()
    def filla(self):
        for i in range(10):
            self.a[str(i)] = i

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