Python __init__方法丢失了自我指针。 很奇怪

Question

class RectangularRoom(object):
    """
    A RectangularRoom represents a rectangular region containing clean or dirty
    tiles.

    A room has a width and a height and contains (width * height) tiles. At any
    particular time, each of these tiles is either clean or dirty.
    """

    class Tile:
        def __init__(self,tilewidth,tileheight):
            self.tilewidth=tilewidth
            self.tileheight=tileheight
            self.isclean=false

    def __init__(self, initwidth,initheight):
        """
        Initializes a rectangular room with the specified width and height.

        Initially, no tiles in the room have been cleaned.

        width: an integer > 0
        height: an integer > 0
        """
        self.width=initwidth
        self.height=initheight
        self.tileslist=[]
        for i in range(self.width+1):
            for j in range(self.height+1):
                tileslist.add(Tile(i,j))

In the above code, in the line for j in range(self.height+1): , the self pointer is lost, as I found in pdb debugger

->for j in range(self.height+1):
(Pdb) p self
<ps2a.RectangularRoom object at 0x7f925c1d10d0>
(Pdb) s
NameError: "global name 'height' is not defined"
> <string>(1)<module>()->None
(Pdb) p self
*** NameError: NameError("name 'self' is not defined",)
(Pdb) $

I found that to be very strange (even alienlike). Any thoughts?

Answer 1

You changed your source code while running the script . Restart your Python session, the source and actual bytecode being run are out of sync. This is why you get a NameError exception for a global name height , while your source code is using an attribute instead.

Tools like pdb load the source code for listing lines on demand , while Python only loads the code once at the start, compiles it into bytecode and runs that. So you started with a line like for j in range(height+1): , started Python with that, saved a new version with self. added, and then when you got to the loop in the debugger, pdb loaded that changed line from disk.

Once the exception is thrown, you are dropped out of the __init__ method context; you are now at <string>(1)<module>()->None , not your for loop. There is no self local name in that scope.