multi threading python/ruby vs java?
philosodad is not wrong to point out the constraint that the GIL presents.  I won't speak for Ruby, but I am sure that it's safe to assume that when you refer to Python that you are in fact referring to the canonical cPython implementation.  
In the case of cPython, the GIL matters most if you want to parallelize computationally intensive operations implemented in Python (as in not in C extensions where the GIL can be released).
However, when you are writing a non-intensive I/O-bound application such as a chat program, the efficiency of the threading implementation really just doesn't matter all that much.
i wonder if the multi threading in python/ruby is equivalent to the one in java?
by that i mean, is it as efficient?
cause if you want to create a chat application that use comet technology i know that you have to use multi threading.
does this mean that i can use python or ruby for that or is it better with java?
thanks