Is there a difference between assertEquals and assertEqual in the python unittest.TestCase?

And if there is not, why are there two functions? Only for convenience?

Actually, in Python 2.6, both assertEqual and assertEquals are convenience aliases to failUnlessEqual. The source declares them thus:

# Synonyms for assertion methods
assertEqual = assertEquals = failUnlessEqual

In Python 3, to your point, failUnlessEqual is explicitly deprecated. assertEquals carries this comment :-)

# Synonyms for assertion methods
# The plurals are undocumented.  Keep them that way to discourage use.
# Do not add more.  Do not remove.
# Going through a deprecation cycle on these would annoy many people.

So, the upshot appears to be that you should use whatever you like for Python 2.x, but tend toward assertEqual for Python 3.