Import error while importing a file in python

I have two files in the same location namely 'hello-depend.py' and 'second-package.py'

hello-depend.py

 class HelloDepend():

    def depend():

         print "depend"

second-package.py

from hello-depend import HelloDepend

 class SecondPackage():

    def second():

       print "second"

       h = HelloDepend()

       h.depend()


 if \__name__ == '\__main__':

    s = SecondPackage()

    s.second()

I need to create object for hello-depend.py from second-package.py. i tied with above method. But i am getting 'syntax error' while importing 'hello-depend'.

Error:

File "second-package.py", line 1

import hello-depend

            ^

SyntaxError: invalid syntax

So i tried with below method.

import importlib

importlib.import_module('hello-depend')

but i am getting "global name 'HelloDepend' not defined'

Please help me in solving this.

Note: I need to do this without changing file name.