type(), isinstance()

In [1]: a = [1,2]

In [2]: type( a) is list
Out[2]: True

In [3]: isinstance(a, list)
Out[3]: True

In [4]: a = u'abc'

In [5]: isinstance(a, (str, unicode))
Out[5]: True

See section 5.5 for an example of how to find the class of an object.