Changing the private variables content

MRAB python at mrabarnett.plus.com
Wed Jul 22 15:12:18 CEST 2009


Ryniek90 wrote:
>>
>> ------------------------------------------------------------------------
>>
>> Temat:
>> Re: Changing the private variables content
>> Od:
>> Gary Herron <gherron at islandtraining.com>
>> Data:
>> Tue, 21 Jul 2009 14:14:44 -0700
>> Do:
>> Ryniek90 <ryniek90 at gmail.com>
>>
>> Do:
>> Ryniek90 <ryniek90 at gmail.com>
>> Kopia:
>> python-list at python.org
>>
>>
>> Ryniek90 wrote:
>>> Hi.
>>> I'm writing some class, and decided to use inside private method and 
>>> some private variables. While with method i haven't got any problem's 
>>> with variables i have.
>>> Maybe some example.
>>> A class with private method and private variable:
>>>
>>> "
>>> >>> class Secret(object):
>>>    #
>>>    def __init__(self):
>>>        self._number = 1
>>>    #
>>>    def _secret(self):
>>>        print self._number
>>>    def showit(self):
>>>        print "Secret number is:\n"
>>>        self._secret()
>>>
>>> >>> sec = Secret()
>>> >>> sec.showit()
>>> Secret number is:
>>>
>>> 1
>>> >>> sec._number
>>> 1
>>> >>> sec._number = 2
>>> >>> sec._number
>>> 2
>>> >>> sec._number += 3
>>> >>> sec._number
>>> 5
>>> >>>
>>> "
>>>
>>> As You can see, i made class with private method and private variable 
>>> inside __init__ constructor. I've changed also the variable value, 
>>> but outside class.
>>> I've got problem with changing some variable value _inside__my_ 
>>> class, which i'm writing.
>>
>> Not sure this is what you are asking, but a method (which is how I 
>> interpret "_inside__my_ class") changes the value by normal assignment 
>> like this:
>>
>> class Secret(object):
>>  ...
>>  def SetNumber(self,value):
>>    self._number = value
>>
>> Is that what you were asking?
>>
>>
>> Gary Herron
>>
>>
>>
>>> I've searched over google, some tuts with topics about operations on 
>>> private variables, but didn't found anything - only how to make them, 
>>> but no how to assign new objects/override them with new content (and 
>>> other advanced and helpful options).
>>>
>>> If someone could help me, it would be great.
>>>
>>> Thanks.
>>
>>
> 
> 
> Thanks for hint, but looks like i can't do what i want.
> 
> Maybe i show You my class:
> 
> "
> 
> class ModPrint(object):
>      u"""
>    This will be the doc.
>    """
>      def __init__(self):
>              #Assign the Python installation directory - sys.exec_prefix 
> - to variable
>        self._default_search_path=sys.exec_prefix
>        self._chosen_module = ''
>        self._user_search_path = ''
>        self._this_module = ''
>          def _SetVar(self, attr, val):
>        self.attr = val            def _search_for_module(self, *args):
>              """Private method which walks through default Python 
> installation directories, and search for prefered module."""
>              #walking thru all directories available in path 
> '_user_search_path'
>        for root, dirs, files in os.walk(self._user_search_path):
>            for f in files:
>                              #if found file 'f' is THAT module,
>                #full path to THAT file is assigned to variable
>                if f == ("%s.py" % self._chosen_module):
>                    self._SetVar(self._this_module, os.path.join(root, f))
>                                        def print_module(self, 
> _chosen_module='', _user_search_path='', 
> _default_search_path=sys.exec_prefix,):
>              """Reads module chosen by user, and returns full content of 
> this module, as it is."""
>                    #if custom search path hasn't been assigned,
>        #default path is being assigned as custom path
>        if self._user_search_path == '':
>            self._user_search_path = self._default_search_path
>                  #using private method '_search_for_module' with 'self.' 
> preffix
>        #to search for prefered module
>        self._search_for_module(_chosen_module, _user_search_path)
>              #opening prefered module with read-only binary mode
>        #and assigning it to 'module_open' variable
>        module_open = open(self._this_module, 'rb')
>              #reading this file and assigning it to variable
>        module_text = module_open.read()
>              #closing read file; the read content is still available
>        #it's stored in variable 'module_text'
>        module_open.close()
>              #returning the read content
>        return module_text
> 
> "
> 
> When i use this class in Python IDLE, i've got this error:
> "
>  >>> mod = ModPrint()
>  >>> import socket
>  >>> mod.print_module('socket')
> 
> Traceback (most recent call last):
>  File "<pyshell#60>", line 1, in <module>
>    mod.print_module('socket')
>  File "<pyshell#57>", line 48, in print_module
>    module_open = open(self._this_module, 'rb')
> IOError: [Errno 2] No such file or directory: ''
>  >>>
> "
> 
> As You can see, i can't assign the new value "os.path.join(root, f)" to 
> the 'self._this_module variable'.
> So for sure i've made some mistake in method:
> 
> "
> def _SetVar(self, attr, val):
>        self.attr = val   "
> When i've changed private variables to normal, stored in class (in 
> __init__ method), it was the same situation - i couldn't change this 
> variable value.
> 
> "
>  >>> mod = ModPrint()
>  >>> mod.print_module('os')
> 
> Traceback (most recent call last):
>  File "<pyshell#72>", line 1, in <module>
>    mod.print_module('os')
>  File "<pyshell#64>", line 48, in print_module
>    module_open = open(self.this_module, 'rb')
> IOError: [Errno 2] No such file or directory: ''
>  >>>
> "
> 
> Thanks i someone could help me, give some hint.

What is the point of the _SetVar method?

Instead of:

     self._SetVar(self._this_module, os.path.join(root, f))

just do:

     self._this_module = os.path.join(root, f)

(unless I'm misunderstanding what you're trying to do!)



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