[Tutor] Help understanding classes

[Bo Morris]

Thank you Alan and Danny. It amazes me at the lengths you guys, as well as everyone else who contributes,  will go to to help explain things to us; it is greatly appreciated!

Alan, I decided to dumb down the learning classes just a little. By this I mean, I am not using Tkinter to learn classes. I am using one of the examples from your website, which I did change it just a little. I figured, I am having a hard time wrapping my head around classes and Tkinter would just add to the confusion.

So, I have the below code. When I run this from terminal, it obviously prints "This is a test." If I may, break the code down and ask questions as it pertains to the code?

#################
class Message:
    def __init__(self, aString):
        self.text = aString

    def printIt(self):
        print self.text

m = Message("This is a test")
m.printIt()

##################

With the first part...
class Message:
    def __init__(self, aString):
        self.text = aString
Will I always use "_init_" when defining the first function in a class? I noticed on your website, you created a class where you did not use "_init_" (see below). Was this because you did not define a function?
class BalanceError(Exception):
      value = "Sorry you only have $%6.2f in your account"

I noticed that I can change "text" to anything and I still get the same results by running the code; I changed them to "blah" just as a test.

When I define a function in a class, will I always use "self" as the first entry in the parenthesis?

On the next part...
m = Message("This is a test")
m.printIt()
I noticed I cannot run "printIt()" unless I make it an object i.e. "m = Message("This is a test")...?"
I noticed I could change "m = Message("This is a test")" to "m = Message(raw_input())," which works.
What if I wanted to create a function in Message that receives text from another function and then prints that text instead of the text from  "m = Message("This is a test")...; can I pass or return values to another function inside a class? The"self" is really throwing me off, when I think about creating different functions that do misc things just to practice. For example, I have a function that kills a Linux program. I just don't see how to rethink that function to where it could be defined in a class?
def kill_proc(process1):
    i = psutil.Popen(["ps", "cax"], stdout=PIPE)
    for proc in psutil.process_iter():
        if proc.name(process1):
            proc.kill()

Would it be something like...?
class processKiller:

    def _init_(self):

    def kill_proc(self, process1):
        i = psutil.Popen(["ps", "cax"], stdout=PIPE)
        for proc in psutil.process_iter():
            if proc.name(process1):
                proc.kill()
Then outside of the class, call it like so...?
p = processKiller()
p.proc.kill()

Again, I am just practicing, trying to wrap my head around classes and understand how to create and use them.

Oh yeah, Alan I preordered your new book maybe a month or so ago. Any word on when it will be released and shipped?

Again, thanks.





















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