How to catch error messages in ftplib?

[JL]

I repost the original code segment to make it more complete;

    from ftplib import FTP
    try:
        session = FTP(ftp_server_ip,ftp_user,ftp_password)
        file = open(filename,'rb') # file to send    
        session.storbinary('STOR ' +  filename, file) # send the file
    except Exception, errObj:
        print Exception
        print errObj
    file.close() # close file and FTP
    session.quit()

On Tuesday, November 19, 2013 6:18:07 PM UTC+8, JL wrote:
> I have the following code;
> 
> 
> 
>     try:
> 
>         session = FTP(ftp_server_ip,ftp_user,ftp_password)
> 
>         file = open(filename,'rb') # file to send    
> 
>         session.storbinary('STOR ' +  filename, file) # send the file
> 
>     except Exception, errObj:
> 
>         print Exception
> 
>         print errObj
> 
>     file.close() # close file and FTP
> 
>     session.quit()
> 
> 
> 
> I deliberately placed an invalid ip address for the ftp_server_ip to see whether error messages can be caught. However, no exception was thrown. Can someone more experienced point to me what did I do wrong?
> 
> 
> 
> Thank you.