question for the part location of multipart message

[Frank Hwa]

Hello

For a multipart message, is text/plain part always in the first 
location?
I just want to extract the plain text body of a message. I use the code 
below (python), but was not very sure.

b = email.message_from_string(x)

if b.is_multipart():
    for part in b.get_payload():
        print part.get_payload()
        break
else:
    print b.get_payload()


Thank you.