Fixed assertion of list with None in the logging agent

[drmargarido]

List comparisons with None to check if they are empty or contain stuff can be incorrect. So I initialized the lastobs to an empty list, and checked if the list has any element with any().

Resolves issue -> #234 LoggingAgent throws ValueError.

[drmargarido]

To reproduce the error you can run this project -> Gamesbeater

NOTE: You need to use the main pybrain repository, instead of my fork which is listed in the dependencies section.

[mlk621]

I have a system environment version of pybrain with the latest pybrain version that runs fine and does not throw this error, however, when I created my own virtual environment and updated versions of various packages, etc. then I am getting this error as well. I am not sure why that is happening since my system version is still a recent version of python.

I suggest a correction to this fix, that instead assert self.lastobs != None in logging.py should be changed to assert self.lastobs is not None instead of initializing an empty list, as you suggest.

The reason for this is that an Environment object's getSensors() method is set to return a numpy array of doubles. It will throw an an error if this is not the case. If you track that what will be returned by getSenstors() from environment.py to getObservation() in task.py to experiment.py's _oneInteraction() method where it calls the agent's integrateObservation() function, this is where we see that self.lastobs is set from the current tasks getObservation() method. Therefore, when _oneInteraction() gets to the line sef.agent.giveReward(reward), then an error is produced by the line we are having the error with assert self.lastobs != None.

Now, numpy arrays have a .any() option as you are suggesting with the empty list, however, this is checking things element-wise to return True/False (see numpy documentation). What we want is to jsut check whether lastobs is not None, meaning it is a numpy array of doubles. I did some testing and assert self.lastobs is not None does what we want, so I suggest this be the fix for this error.