How to import module when module name has a '-' dash or hyphen in it?

Starting from Python 3.1, you can use importlib :

import importlib  
foobar = importlib.import_module("foo-bar")

( https://docs.python.org/3/library/importlib.html )

In Python 2, you can't. foo-bar is not an identifier. rename the file to foo_bar.py

It's possible since Python 3.1+, see Julien's answer.

If import is not your goal (as in: you don't care what happens with sys.modules, you don't need it to import itself), just getting all of the file's globals into your own scope, you can use execfile

# contents of foo-bar.py
baz = 'quux'

>>> execfile('foo-bar.py')
>>> baz
'quux'
>>> 

Solution: If you can't rename the module to match Python naming conventions, create a new module to act as an intermediary:

New module foo_proxy.py:

 tmp = __import__('foo-bar')
 globals().update(vars(tmp))

Module doing the import main.py:

 from foo_proxy import * 

If you can't rename the original file, you could also use a symlink:

ln -s foo-bar.py foo_bar.py

Then you can just do:

from foo_bar import *