Serhiy collected interesting numbers, copy/paste of this message:
http://bugs.python.org/issue28637#msg280380

On my computer:

Importing empty module: 160 us
Creating empty class: 30 us
Creating empty function: 0.16 us
Creating empty Enum/IntEnum: 125/150 us
Creating Enum/IntEnum member: 25/27 us
Creating empty namedtuple: 600 us
Creating namedtuple member: 50 us
Importing the itertools module: 40 us
Importing the io module: 900 us
Importing the os module: 1600 us
Importing the functools module: 2100 us
Importing the re module (with all sre submodules): 3300 us
Python startup time: 43000 us