Re: [matplotlib-devel] cbook.py, maxdict class key checking on __setitem__

[Eric F. <ef...@ha...>]

Ryanitus wrote:
> I may have found a bug in the __setitem__ method of the maxdict class.
> 

Fixed--thanks for pointing it out.

Eric

> Since a dictionary is a mapping class, if an item is set that already
> exists, it overwrites the previous.  However, you are still appending that
> item to _killkeys regardless.
> 
> In the case where 2 items with the same key were added and later removed due
> to size constraints, the line in bold would throw an exception on the second
> call.
> 
> By checking for the key existance, you handle that situation gracefully. 
> The item can still be removed from _killkeys, since it's the next to go
> anyway.
> 
> Ryan
> 
> Original code (circa line 776):
> 
>         if len(self)>=self.maxsize:
>             del self[self._killkeys[0]]
>             del self._killkeys[0]
>         dict.__setitem__(self, k, v)
>         self._killkeys.append(k)
> 
> Possible solution:
> 
>         if len(self)>=self.maxsize:
>             if self.has_key(self._killkeys[0]):
>                 del self[self._killkeys[0]]
>             del self._killkeys[0]
>         dict.__setitem__(self, k, v)
>         self._killkeys.append(k)
> 
> 
>