def is_number(num):
    
    """Tests to see if arg is number. """
    
    try:
        #Try to convert the input. 
        float(num)
        
        #If successful, returns true.
        return True
        
    except:
        #Silently ignores any exception.
        pass
    
    #If this point was reached, the input is not a number and the function
    #will return False.
    return False