import pprint

class A:
    print dir()
    pprint.pprint(globals())

A()

>>> a = 1
>>> 'a' in dir() and 'a' in sys.modules
False
>>> 'sys' in dir() and 'sys' in sys.modules
True
>>>

>>> import sys
>>> import os
>>> os = 1
>>> 'os' in dir() and 'os' in sys.modules
True
>>> type(1)
<class 'int'>
>>> type(sys)
<class 'module'>
>>> isinstance(1, int)
True
>>> isinstance(sys, module)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'module' is not defined
>>>

>>> import os
>>> a = os
>>> type(a)
<class 'module'>
>>> import types
>>> 'a' in dir() and isinstance(a, types.ModuleType)
True
>>> b = 1
>>> 'b' in dir() and isinstance(b, types.ModuleType)
False
>>>