Python bug???

Engines and Middleware Programming

Started by macktruck6666 July 14, 2010 10:14 PM

6 comments, last by Joviex 13 years, 9 months ago

macktruck6666

100

Author

July 14, 2010 10:14 PM

The problem is that I expect the output to be:
0
0
instead it is:
0
1

Is there a solution to the following code?

class Menu:   subMenuList = []   def addSubMenu(self, newSubMenu):      print len(newSubMenu.subMenuList)      self.subMenuList.append(newSubMenu)      print len(newSubMenu.subMenuList)mainMenu = Menu()subMenu = Menu()mainMenu.addSubMenu(subMenu)

[Edited by - macktruck6666 on July 14, 2010 10:34:48 PM]

Roboguy

794

July 14, 2010 10:30 PM

append adds a new element to the list, which, in this case, is [].
So the list looks like this after the append: [[]]. That's a list containing one element; the one element being [].
Also, you can use the [code] and tags in the forums to preserve indentation. Look here: GDNet Forums FAQ

http://www.roboguy.net(WIP) - lisperati - SICP - Haskell - Python - OCaml - Lambda the Ultimate - Good Math, Bad Math - Wiki (not Wikipedia) - Pure - Term-Rewriting Functional Language

macktruck6666

100

Author

July 14, 2010 10:46 PM

The item that is added is actually a menu object. I've tested it.
So, mainMenu.subMenuList looks like [menu object]
and, subMenu.subMenuList looks like [menu object]
and, subMenu.subMenuList[0].subMenuList[0].subMenuList looks like [menu object]

Sneftel

1,788

July 14, 2010 11:06 PM

Riight? So after the append, newSubMenu.subMenuList contains one item. Forget the nesting hoohah -- why would you expect a list to be empty, when you just put something in it?

macktruck6666

100

Author

July 14, 2010 11:20 PM

I put something into Main.subMenuList not into subMenu.subMenuList
or in context of addSubMenu method
I put something into self.subMenuList not into self.subMenuList[0].subMenuList

Oluseyi

2,123

July 15, 2010 01:07 AM

Quote:Original post by macktruck6666
I put something into Main.subMenuList not into subMenu.subMenuList
or in context of addSubMenu method
I put something into self.subMenuList not into self.subMenuList[0].subMenuList

Wrong.

Hodgman

52,717

July 15, 2010 01:34 AM

Ah, I didn't understand what was going on here either.

So if I debluntize Ollies reply, the subMenuList member doesn't actually belong to either of the Menu objects; it belongs to the Menu class and is therefore shared by both objects.

. 22 Racing Series .

Joviex

250

July 22, 2010 01:18 AM

Quote:Original post by Hodgman
Ah, I didn't understand what was going on here either.

So if I debluntize Ollies reply, the subMenuList member doesn't actually belong to either of the Menu objects; it belongs to the Menu class and is therefore shared by both objects.

Correct!

class Menu:   def __init__(self):      self.subMenuList = []   def addSubMenu(self, newSubMenu):      print len(newSubMenu.subMenuList)      self.subMenuList.append(newSubMenu)      print len(newSubMenu.subMenuList)mainMenu = Menu()subMenu = Menu()mainMenu.addSubMenu(subMenu)

Python bug???

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Python bug???

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