"parent" in a class __init__ def?

[bruno at modulix]

Ray Schumacher wrote:
> What is the feeling on using "parent" in a class definition

"parent" is just a name. What is the semantic for this name ? Parent
class (ie: superclass) ? Container ? Else ?

> that class
> methods 

Takes care, "class method" has a very defined meaning in Python - a
class method is a method that takes the class object - not the instance
- as first param.

> can refer to, vs. some other organization ?
> Should all relevant objects/vars just be passed into the method as needed?

There's no absolute rule about this - at most some guidelines :
- What constitutes the state of an object should be an attribute of the
object.
- What is not part of the state and is only used for a given operation
should be passed as param.

> It seems like including "parent" in the class def is just like a class
> variable,

Here again, "class variable" has a well defined meaning in Python: it's
an attribute of the class object itself, that is shared by all instances
of the class.

> which most do not recommend.
> 
> An example:
> class LXSerial:

do yourself a favour : use new-style classes whenever possible.

>     def __init__(self, parent, debug=False):
>     ...
>     def connect(self, port, baud=9600, ptimeout=10):
>         if self.debug:
>             self.connectedPort = StringIO.StringIO(':A#')
>         else:
>             if self.parent.model=='LX200GPS': ptimeout = 240
>             ...

We still don't know what's the semantic for this 'parent'. But anyway,
having this test on self.parent.model smells of a design error. If the
timeout value depends on the 'parent' object, then it's clearly a
responsability of this parent object to know that value. Your code here
should read:

  def connect(self, ....)
    # ...
    ptimeout = self.parent.timeout
    # ...

You may also want to have a look at the strategy pattern, to avoid
cluttering your code with "if self.debug"...

wrt/ your original question, I don't see how one could give a sound
answer without knowing more about this "parent" object and it's
relationship with the LXSerial class/instance of.

-- 
bruno desthuilliers
python -c "print '@'.join(['.'.join([w[::-1] for w in p.split('.')]) for
p in 'onurb at xiludom.gro'.split('@')])"