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-   -   Re: What is the naming convention for accessor of a 'private'variable? (http://www.velocityreviews.com/forums/t705834-re-what-is-the-naming-convention-for-accessor-of-a-privatevariable.html)

Peng Yu 11-19-2009 03:04 AM

Re: What is the naming convention for accessor of a 'private'variable?
 
On Wed, Nov 18, 2009 at 8:47 PM, Chris Rebert <clp2@rebertia.com> wrote:
> On Wed, Nov 18, 2009 at 6:27 PM, Peng Yu <pengyu.ut@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."

Lie Ryan 11-22-2009 06:53 PM

Re: What is the naming convention for accessor of a 'private' variable?
 
Peng Yu wrote:
> On Wed, Nov 18, 2009 at 8:47 PM, Chris Rebert <clp2@rebertia.com> wrote:
>> On Wed, Nov 18, 2009 at 6:27 PM, Peng Yu <pengyu.ut@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).


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