One reason we usually suggest that people don't use star imports is that it is too easy to shadow a builtin or overwrite an existing global.  Momma Gump always used to say, "import star is like a box of chocolates, you never know what you've going to get".

>>> from os import *
Warning (from warnings module):
  File "__main__", line 1
ImportWarning: The 'open' variable in the 'os' module shadows a variable in the 'builtins' module

>>> alpha = 2.0
>>> beta = 3.0
>>> gamma = 4.5
>>> delta = 5.5
>>> from math import *
>>> from os import *
Warning (from warnings module):
  File "__main__", line 8
ImportWarning: The 'gamma' variable in the 'math' overwrites an existing variable in the globals.