Correct Way to Write in Python

[Sagar Varule]

On Saturday, August 3, 2013 1:50:41 PM UTC+5:30, Steven D'Aprano wrote:
> On Fri, 02 Aug 2013 23:18:47 -0700, punk.sagar wrote:
> 
> 
> 
> > Hi All,
> 
> > 
> 
> > Im new to Python. Im coming from C# background and want to learn Python.
> 
> > I was used to do following thing in C# in my previous experiences. I
> 
> > want to know how do I implement below example in Python. How these
> 
> > things are done in Python. 
> 
> 
> 
> I am not an expert on C#, but I'll try to translate the following code to 
> 
> Python.
> 
> 
> 
> 
> 
> > [code]
> 
> > public class Bank
> 
> > {
> 
> > 	
> 
> > 	public List<Customer> lstCustomers = new List<Customer>();
> 
> > 	private string micrcode;
> 
> > 	
> 
> > 	public void Bank()
> 
> > 	{
> 
> > 		customer
> 
> > 	}
> 
> > 
> 
> > }
> 
> > 
> 
> > public class Customer
> 
> > {
> 
> > 	private srting customername;
> 
> > 	public string CustomerName
> 
> 
> 
> Do you mean "private string" rather than "private srting"?
> 
> 
> 
> 
> 
> > 	{
> 
> > 		get { return customername; }
> 
> > 		set { customername = value; }
> 
> > 	}
> 
> > }
> 
> > 
> 
> > main()
> 
> > {
> 
> > 	Customer objCustomer = new Customer;
> 
> > 	objCustomer.CustomerName = "XYZ"
> 
> > 	
> 
> > 	Bank objBank = new Bank();
> 
> > 	objBank.lstCustomer.Add(objCustomer);
> 
> > 	
> 
> > }
> 
> > [/code]
> 
> 
> 
> 
> 
> Here is a literally translation, as best as I can understand the C# code. 
> 
> (But note that this is not the best Python code.)
> 
> 
> 
> 
> 
> class Bank:
> 
>     def __init__(self):
> 
>         self.lstCustomers = []  # Empty list of customers.
> 
>         self._micrcode = ''  # Does this actually get used?
> 
> 
> 
> class Customer:
> 
>     def __init__(self):
> 
>         self._customername = ''
> 
> 
> 
>     @property
> 
>     def CustomerName(self):
> 
>         return self._customername
> 
> 
> 
>     @CustomerName.setter
> 
>     def CustomerName(self, value):
> 
>         if not instance(value, str):
> 
>             raise TypeError('names must be strings')
> 
>         self._customername = value
> 
> 
> 
> 
> 
> if __name__ == '__main__':
> 
>     # Running as a script, call the main function.
> 
>     objCustomer = Customer()
> 
>     objCustomer.CustomerName = "XYZ"
> 
> 
> 
>     objBank = Bank()
> 
>     objBank.lstCustomers.append(objCustomer)
> 
> 
> 
> 
> 
> 
> 
> But this isn't how I would write it in Python. For starters, our naming 
> 
> conventions are different. Everything in Python is an object, even simple 
> 
> types like ints and strings, and even classes, so it isn't meaningful to 
> 
> prefix instances with "obj".
> 
> 
> 
> We tend to avoid anything which even vaguely looks like Hungarian 
> 
> Notation, so "lstCustomer" is right out. Instead, we use plural for 
> 
> collections (lists, sets, dicts, whatever) of things, and singular for 
> 
> individual instances.
> 
> 
> 
> Also, while we can use the "property" decorator to make computed 
> 
> attributes, we very rarely do just to enforce private/public variables. 
> 
> Our philosophy is, if you want to shoot yourself in the foot, we're not 
> 
> going to stop you. (People spend far too much time trying to work around 
> 
> private names in other languages for Python to spend too much effort in 
> 
> this area.) Instead, we have "private by convention": names starting with 
> 
> a single underscore are "private", so don't touch them, and if you do, 
> 
> you have nobody but yourself to blame when you shoot yourself in the foot.
> 
> 
> 
> Similarly, the language doesn't spend much time enforcing type 
> 
> restrictions. Python is a dynamic language, and type restrictions go 
> 
> against that philosophy. If you have a good reason to put a non-string as 
> 
> the customer name, you can do so, but don't come crying to me if you 
> 
> break your code. So here is how I would write the above:
> 
> 
> 
> 
> 
> 
> 
> class Bank:
> 
>     def __init__(self):
> 
>         self.customers = []
> 
>         self._micrcode = ''  # Does this actually get used?
> 
> 
> 
> class Customer:
> 
>     def __init__(self, name):
> 
>         # This type-check is optional.
> 
>         if not instance(name, str):
> 
>             raise TypeError('names must be strings')
> 
>         self.name = name
> 
> 
> 
> 
> 
> if __name__ == '__main__':
> 
>     # Running as a script, call the main function.
> 
>     customer = Customer("XYX")
> 
> 
> 
>     bank = Bank()
> 
>     bank.customers.append(customer)
> 
> 
> 
> 
> 
> The above is still not what I call professional quality -- no doc strings 
> 
> (documentation), and the bank doesn't actually do anything, but it's a 
> 
> start.
> 
> 
> 
> 
> 
> -- 
> 
> Steven

Thanks Steven for your Time and Effort. You have cleared many doubts and concepts for that I was struggling, since I started learning python. But I am falling in love for Python. Your explanation for private and public access modifier was awesome as I was having harding time finding why we dont have access modifier for python....Thanks a lot