essentially, the generalization of
    
    arg if arg else default

    or

    func(arg) if arg else default

def conv(arg,default=None,func=None):
    '''
    essentially, the generalization of
    
    arg if arg else default

    or

    func(arg) if arg else default
    '''
    if func:
        return func(arg) if arg else default;
    else:
        return arg if arg else default;