python的私人變數解析

在內的內部定義並使用，外部無法訪問，以雙底線作為前作，定義後被python轉為
_classname__變數名了

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In [1]: class aa:
   ...: __x = 12 #私人變數_ _x
   ...: def px(self):
   ...: print 'private __x', aa.__x #內部訪問
   ...:

In [2]: a = aa()

In [3]: a.px()
private __x 12

In [4]: dir(a)
Out[4]: ['__doc__', '__module__', '_aa__x', 'px'] # map成_classname__變數名了

In [5]: a.__x = 13#執行個體對象a的執行個體變數

In [6]: dir(a)
Out[6]: ['__doc__', '__module__', '__x', '_aa__x', 'px']

In [7]: print a.__x
13

In [8]:In [8]: print aa.__x
---------------------------------------------------------------------------
AttributeError Traceback (most recent call last)
<ipython-input-8-34f87438b5b5> in <module>()
----> 1 print aa.__x

AttributeError: class aa has no attribute '__x'

In [9]:
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