What is the naming convention for accessor of a 'private' variable?

[Lie Ryan]

Peng Yu wrote:
> On Wed, Nov 18, 2009 at 8:47 PM, Chris Rebert <clp2 at rebertia.com> wrote:
>> On Wed, Nov 18, 2009 at 6:27 PM, Peng Yu <pengyu.ut at gmail.com> wrote:
>>> http://www.python.org/dev/peps/pep-0008/
>>>
>>> The above webpage states the following naming convention. Such a
>>> variable can be an internal variable in a class. I'm wondering what is
>>> the naming convention for the method that access such variable.
>>>
>>>    - _single_leading_underscore: weak "internal use" indicator.  E..g. "from M
>>>      import *" does not import objects whose name starts with an underscore.
>> If there's a method to access the variable, then it's not all that
>> private, is it?
>> Accessor methods are not Pythonic. Just make the attribute public by
>> not prefixing it with an underscore.
>>
>> See also "Python is Not Java":
>> http://dirtsimple.org/2004/12/python-is-not-java.html
> 
> I don't quite understand the following paragraph from the above
> webpage. Would you please give me an example to help me understand it?
> 
> "Here's what you do. You write a function that contains a function.
> The inner function is a template for the functions that you're writing
> over and over again, but with variables in it for all the things that
> vary from one case of the function to the next. The outer function
> takes parameters that have the same names as those variables, and
> returns the inner function. Then, every place where you'd otherwise be
> writing yet another function, simply call the outer function, and
> assign the return value to the name you want the "duplicated" function
> to appear. Now, if you need to change how the pattern works, you only
> have to change it in one place: the template."

Basically it sums to (pun not intended):

def adder(by):
     def _adder(num):
         return num + by
     return _adder

add4 = adder(4)
add10 = adder(10)
add35 = adder(35)
add1 = adder(1)

in java, you'll need to manually duplicate the code, equivalent to doing:

def add4(num):
     return num + 4
def add10(num):
     return num + 10
def add35(num):
     return num + 35
def add1(num):
     return num + 1

or passes two arguments (which completely misses the point).