Writing a Python Class Give C# Equivalent

Nexusfactor · 07-28-2015, 11:25 AM

I'm attempting to learn Python on my own,so, I got a piece of software I had written in C#, and attempted to re-write it in Python. Given the following class I have a few questions:

C#

Code:

sealed class Message
    {
        private int messageID;
        private string message;
        private ConcurrentBag <Employee> messageFor;
        private Person messageFrom;
        private string calltype;
        private string time;
      
       
        public Message(int iden,string message, Person messageFrom, string calltype,string time)
        {
            this.MessageIdentification = iden;
            this.messageFor = new ConcurrentBag<Employee>();
            this.Note = message;
            this.MessageFrom = messageFrom;
            this.CallType = calltype;
            this.MessageTime = time;
        }
    
        public ICollection<Employee> ReturnMessageFor
        {
            get
            {
                return messageFor.ToArray();
            }
    
        }

1. In my class I have a thread-safe collection called messageFor, is there an equivalent in Python? If so, how do I implement it in a python class?

2. I also have a getter for my thread-safe collection? How would I go about doing the same in Python?

3. Does Python have an EqualsTo method to test equality between objects? Or the
equivalent of this in Python?

Code:

  public override bool Equals(object obj)
            {
                if (obj == null)
                {
                    return false;
                }
    
                Message testEquals = obj as Message;
    
                if((System.Object)testEquals == null)
                {
                    return false;
                }
    
                return (this.messageID == testEquals.messageID) && (this.message == testEquals.message) && (this.messageFor == testEquals.messageFor) && (this.messageFrom == testEquals.messageFrom) && (this.calltype == testEquals.calltype);
                
            }
    
            public bool Equals(Message p)
            {
                if ((Object)p == null)
                {
                    return false;
                }
    
                return (this.messageID == p.messageID) && (this.message == p.message) && (this.messageFor == p.messageFor) && (this.messageFrom == p.messageFrom) && (this.calltype == p.calltype);
    
            }

4. Can you make it sealed, so that no one can inherit from it?

What I've got so far:

Code:

class Message:
 

       def __init__(self, messageID, message, callType):
        
          self.messageID = messageID
          self.message = message
          self.callType = callType

rtmistler · 07-28-2015, 12:15 PM

Quote:

Originally Posted by Nexusfactor

]I'm trying to learn Python on my own, so I got a copy of class I'd written in C# and attempt to write it in Python. I've got two questions:

1. How would you write this C# Class in python? My problem is when it comes to the thread-safe collection messageFor. Does Python have thread-safe collections? If so, how would you implement it as shown above?

2. Does Python have an equalsTo method to test for equality between Objects?

You're starting out with a very involved example. Instead first write something small in Python and grow the concepts to include much of what is represented within your example class. Or you can submit what you have to the python interpreter program you have and see where it complains and then correct the syntax piece by piece. My style here would be to start small and grow my class definition until I got an equivalent. This way whatever concepts needed to be re-designed, I learned them as I went along.

Most persons here will offer various suggestions, but the overall intent is that you make an attempt first rather than copy in a bunch of code an ask people to write an equivalent for you.

dugan · 07-28-2015, 01:01 PM

Here it is, along with some test code.

To match the following:

Code:

namespace Crystal_Message

Simply put the code in a module named "Crystal_Message.py".

The only method that needed the C# container's thread safety was addEmployee. I added locking to that method, and made the method itself thread-safe.

You will also note the overriding of the __eq__ method (equals operator) and the __hash__ method (GetHashCode in C#).

Code:

from cStringIO import StringIO
from threading import Lock

mutex = Lock()


def main():
    # Some test code to make sure it works.
    message1 = Message(1, "message", "Id", "calltype", "time")

    print "message1: ", str(message1)
    print "hash(message1)", hash(message1)

    message2 = Message(1, "message", "Id", "calltype", "time")
    print "hash(message2)", hash(message2)
    print "message1 == message2:", message1 == message2

    message2.addEmployee("Employee1")
    message2.addEmployee("Employee2")
    print "message2: ", str(message2)


class Message(object):
    def __init__(self, iden, message, messageFrom, calltype, time):
        self.MessageID = iden
        self.messageFor = []
        self.Note = message
        self.MessageFrom = messageFrom
        self.CallType = calltype
        self.MessageTime = time

    @property
    def ReturnMessageFor(self):
        return self.messageFor

    @property
    def MessageTime(self):
        return self.time

    @MessageTime.setter
    def MessageTime(self, value):

        if not value:
            raise ValueError("Need to Provide Time")

        self.time = value

    @property
    def MessageIdentification(self):
        return self.MessageID

    @MessageIdentification.setter
    def MessageIdentification(self, value):

        if value == 0:
            raise ValueError("Must have Message ID")

        self.MessageID = value

    @property
    def Note(self):
        return self.message

    @Note.setter
    def Note(self, value):
        if not value:
            raise ValueError("Must Have a Message")

        self.message = value

    # I removed the MessageFrom property, as it has no value. It's just an attribute now.

    @property
    def CallType(self):
        return self.calltype

    @CallType.setter
    def CallType(self, value):
        if not value:
            raise ValueError("Please specify call type")
        self.calltype = value

    def addEmployee(self, add):
        mutex.acquire()
        self.messageFor.append(add)
        mutex.release()

    def __str__(self):
        value = "Message: {} From: {} Call Type: {} For: {} Time: {}".format(
            self.message,
            self.MessageFrom,
            self.calltype,
            self.returnMessageFor(),
            self.time
        )
        return value

    def returnMessageFor(self):
        generate = StringIO()
        for view in self.messageFor:
            generate.write(str(view))
            generate.write(" ")
        return generate.getvalue()

    def __eq__(self, other):
        if not isinstance(other, Message):
            return False

        return all([
            self.MessageID == other.MessageID,
            self.message == other.message,
            self.messageFor == other.messageFor,
            self.MessageFrom == other.MessageFrom,
            self.calltype == other.calltype
        ])

    def __hash__(self):
        return hash(self.MessageID) * 33 ^ hash(self.message) * 33 ^ \
            hash(tuple(self.messageFor)) * 33 ^ hash(self.MessageFrom) * 33 ^ \
            hash(self.calltype)


# Let's try the class out.

if __name__ == '__main__':
    main()

dugan · 07-28-2015, 05:45 PM

Thanks for trimming your code down to the parts you actually need help with. Unfortunately, my reply was to the full version.

I see you've added this:

Quote:

4. Can you make it sealed, so that no one can inherit from it?

The real answer is no.

A Google search for "python sealed class" got me a way to do it, if you really, really want to, but really, the answer is no. That isn't done in Python. Anyway, if you still want to do it, this will work:

http://stackoverflow.com/a/16564232

I believe I've answered everything. Let me know if there's anything that was missed.

sundialsvcs · 07-28-2015, 09:45 PM

Generally speaking, though, the final answer will be: "no."

The C# language is a compiled language that is designed to do things that only such languages do. (For example, if you wanted to write a language interpreter, C# would be a fine language to do it in. I know this because I've done it...)

Python, on the other hand, is designed to be an interpreted environment. While it "supports objects and classes," the scope of its implementation is not designed to be so extensive ... nor would it necessarily be appropriate (or perhaps, even implementable) for it so to be.

As a compiler, C# can generate code to do anything, without affecting itself. When the generated program runs, it's completely free to set up and to maintain any environment it wants. As an interpreter, the Python interpreter is "the actual program that the computer is running," and this doesn't change from Python-run to run, even though the bytecode/source-code being interpreted does.

Nexusfactor · 07-29-2015, 06:12 AM

Quote:

Originally Posted by dugan

Thanks for trimming your code down to the parts you actually need help with. Unfortunately, my reply was to the full version.

I see you've added this:

The real answer is no.

A Google search for "python sealed class" got me a way to do it, if you really, really want to, but really, the answer is no. That isn't done in Python. Anyway, if you still want to do it, this will work:

http://stackoverflow.com/a/16564232

I believe I've answered everything. Let me know if there's anything that was missed.

Many thanks for everything. This is fantastic!

Nexusfactor · 07-29-2015, 08:34 AM

Quote:

Originally Posted by dugan

Thanks for trimming your code down to the parts you actually need help with. Unfortunately, my reply was to the full version.

I see you've added this:

The real answer is no.

A Google search for "python sealed class" got me a way to do it, if you really, really want to, but really, the answer is no. That isn't done in Python. Anyway, if you still want to do it, this will work:

http://stackoverflow.com/a/16564232

I believe I've answered everything. Let me know if there's anything that was missed.

I posted this same question on StackOverFlow, however, no one did what you were able to do, again Thanks. However, at the bottom the last comment, says

Quote:

Don't return False from __eq__ because of the rhs being the wrong type: return NotImplemented instead. Think of it as three value logic: 'yes', 'no' or 'I don't know' - and if you don't know, python might be able to ask the other object if it knows

Do you agree, and how would you implement what the poster was talking about?

dugan · 07-29-2015, 09:23 AM

Quote:

Originally Posted by Nexusfactor

Do you agree, and how would you implement what the poster was talking about?

I don't agree in this case, because the goal is to do the same thing as your C# code, and your C# code returns False if you're comparing the "wrong type".

If I were to implement that, though:

Code:

def __eq__(self, other):
    if not isinstance(other, Message):
        raise NotImplementedError

    return all([
        self.MessageID == other.MessageID,
        self.message == other.message,
        self.messageFor == other.messageFor,
        self.MessageFrom == other.MessageFrom,
        self.calltype == other.calltype
    ])

Nexusfactor · 07-29-2015, 12:01 PM

Quote:

Originally Posted by dugan

I don't agree in this case, because the goal is to do the same thing as your C# code, and your C# code returns False if you're comparing the "wrong type".

If I were to implement that, though:

Code:

def __eq__(self, other):
    if not isinstance(other, Message):
        raise NotImplementedError

    return all([
        self.MessageID == other.MessageID,
        self.message == other.message,
        self.messageFor == other.messageFor,
        self.MessageFrom == other.MessageFrom,
        self.calltype == other.calltype
    ])

Thanks for the code, just for my own understanding, how did you learn Python? School? TextBooks? (If so, what where the titles?) Youtube videos?

dugan · 07-29-2015, 12:04 PM

This was my learn-Python project:

http://duganchen.ca/project/software...tl-mpd-client/

Learning Python was difficult for me, actually. There was one book that did click with me (I think it was by that guy who chose to disappear from the Internet after writing it), but I can't really recall it right now.