Adding tuples to a dictionary

[Maciej Blizi ski]

Thank you for all the answers! My problem is solved even better than I
expected!

@Peter: Yes, the garbage collector was causing the slowdown. Switching
it off sped the program up; each iteration was taking the same amount
of time. I ran collection manually every 10 iterations to control
memory usage.

@Bosko: Right, this example code had a bug, appending to the
dictionary was meant to be one nesting level up.

@Nick: Using a tuple cache is a great advice! My real program's tuples
are even better to cache, as there are roughly about 10 different
tuples that are used as values. Using a tuple cache reduced the memory
consumption by about 3-4 times (I'm telling that by looking at the
gkrellm display).

Thanks!
Maciej