Can any one explain me about data hiding clearly ?

Question

i didn't understand data hiding also with simple example apart from this tutorial in this app

Answer 1

The Basic concept of data hiding is making a member of a object invisible so you can't modify it.
Python doesn't implement this like other languages and you can still access the 'hidden' member if you really want to.
In c++ for example. if you have a private(aka hidden for your example) variable
an instance of that class can not access that variable. It will thow an error.
class AB
{
public:
int x;
protected:
int y;
private:
int z;
};

AB foo; //create an instance of the AB Class
foo.x = 1 //allowed, can access x
foo.z = 1 //error!, can't access z as it's 'hidden' using the private declaration

In python there is no private, protected options. Instead we use a single or double underscore. Many ide's for python may warn if you try to access them however you still can.
a very simplified way to think in python is when you see a single underscore on a variable/method it means you shouldn't access it directly, if you see a double underscore you really shouldn't access it directly...however python assumes you know what your doing if you do want to access it :) because we're grown ups.
same but in python:

class AB(object):
def __init__(self):
self.x = None # public, anyone can access it
self._y = None # you shouldn't touch it
self.__z = None # you really shouldn't touch it
};

foo = AB(); //create an instance of the AB Class
foo.x = 1 //allowed, can access x
foo._y = 2 # allowed
foo.__z = 3 # allowed

You will notice the init function of the class also uses double underscores, this is slightly different but the in the same vain you could try:
foo.__init__()
But really you should never have to do that directly, it is 'hidden' for a reason.
hope that helps and doesn't make it all the more confusing for you!!!
Good luck!