The following may be used within a setup.py file to ensure packages are installed prior to the installation process.

required.py

def is_installed(pkg):
    '''
    Tests if a python module is installed. 
    '''
    try: 
        __import__(pkg)
        return True
    except ImportError:
        return False

def ensure_installed(pkg):
    '''
    Ensures a package is installed. This is done by 
    first testing if a module has already been 
    installed. If the module has not already been 
    installed pip is used to install the module. 
    '''
    if not is_installed(pkg):
        import pip
        pip.main(['install', pkg])
    
    # at this point pkg should be installed
    if not is_installed(pkg):
        print('Sorry, {0} must be installed to proceed.')
        sys.exit(1)