Exploring the newsgroups data
After we download the 20 newsgroups dataset by whatever means we prefer, the data
 object of groups
 is now cached in memory. The data
 object is in the form of a key-value dictionary. Its keys are as follows:
>>> groups.keys()
dict_keys(['data', 'filenames', 'target_names', 'target', 'DESCR'])
The target_names
 key gives the newsgroups names:
>>> groups['target_names']
['alt.atheism', 'comp.graphics', 'comp.os.ms-windows.misc', 'comp.sys.ibm.pc.hardware', 'comp.sys.mac.hardware', 'comp.windows.x', 'misc.forsale', 'rec.autos', 'rec.motorcycles', 'rec.sport.baseball', 'rec.sport.hockey', 'sci.crypt', 'sci.electronics', 'sci.med', 'sci.space', 'soc.religion.christian'...