Python允许带有双下划线前缀的私有类成员。这种技术在模块级别上不起作用，所以我认为这是Dive Into Python中的一个错误。

下面是一个私有类函数的例子:

class foo():
    def bar(self): pass
    def __bar(self): pass

f = foo()
f.bar()   # this call succeeds
f.__bar() # this call fails

这个问题没有得到完全的回答，因为模块私密性并不完全是常规的，而且使用import可能会识别模块私密性，也可能不会，这取决于它的使用方式。

如果你在一个模块中定义了私有名称，这些名称将被导入到任何使用'import module_name'语法的脚本中。因此，假设您在示例中正确定义了模块private， _num，在a.py中，如下所示..

#a.py
_num=1

．．你可以在b.py中使用模块名符号来访问它:

#b.py
import a
...
foo = a._num # 1

要从a.py中只导入非私有对象，你必须使用from语法:

#b.py
from a import *
...
foo = _num # throws NameError: name '_num' is not defined

然而，为了清晰起见，在从模块中导入名称时最好显式，而不是用'*'导入它们:

#b.py
from a import name1 
from a import name2
...

In Python, "privacy" depends on "consenting adults'" levels of agreement - you can't force it (any more than you can in real life;-). A single leading underscore means you're not supposed to access it "from the outside" -- two leading underscores (w/o trailing underscores) carry the message even more forcefully... but, in the end, it still depends on social convention and consensus: Python's introspection is forceful enough that you can't handcuff every other programmer in the world to respect your wishes.

((顺便说一下，虽然这是一个严格保密的秘密，但对于c++来说也是如此:在大多数编译器中，在#包括你的.h文件之前，一个简单的#define private public line就可以让狡猾的编码器对你的“隐私”进行散列…!-))

这是一个古老的问题，但是模块私有(一个下划线)和类私有(两个下划线)被破坏的变量现在都包含在标准文档中:

Python教程»类»私有变量

见PEP8指南:

方法名称和实例变量

Use the function naming rules: lowercase with words separated by underscores as necessary to improve readability. Use one leading underscore only for non-public methods and instance variables. To avoid name clashes with subclasses, use two leading underscores to invoke Python’s name mangling rules. Python mangles these names with the class name: if class Foo has an attribute named __a, it cannot be accessed by Foo.__a. (An insistent user could still gain access by calling Foo._Foo__a.) Generally, double leading underscores should be used only to avoid name conflicts with attributes in classes designed to be subclassed.

为传承而设计

Always decide whether a class’s methods and instance variables (collectively: “attributes”) should be public or non-public. If in doubt, choose non-public; it’s easier to make it public later than to make a public attribute non-public. Public attributes are those that you expect unrelated clients of your class to use, with your commitment to avoid backwards incompatible changes. Non-public attributes are those that are not intended to be used by third parties; you make no guarantees that non-public attributes won’t change or even be removed. We don’t use the term “private” here, since no attribute is really private in Python (without a generally unnecessary amount of work).

对于方法:(我不确定这是否是你想要的)

print_thrice.py

def private(method):
    def methodist(string):
        if __name__ == "__main__":
            method(string)
    return methodist
    
@private
def private_print3(string):
    print(string * 3)

private_print3("Hello ") # output: Hello Hello Hello

other_file.py

from print_thrice import private_print3
private_print3("Hello From Another File? ") # no output

这可能不是一个完美的解决方案，因为您仍然可以“看到”和/或“调用”该方法。不管怎样，它不会执行。