Python smtplib cannot attach multiple mimetext

I can't able to figure out why my python code can't attach HTML table (part2) and plain sentence(part1) at a same email. I tried commenting one line message.attach(part2) and it works vice versa. There's something wrong with the message object.

    port = 587 # For starttls
    smtp_server = "smtp.gmail.com"
    sender_email = "xyz@gmail.com"
    receiver_email = ["abc@qwer.com","def@gmail.com"]
    password = getpass.getpass()
    message = MIMEMultipart("alternative")
    message["From"] = sender_email
    message["To"] = ", ".join(receiver_email)
    message["Subject"] = "Report"

    # Create the plain-text and HTML version of your message
    pd.read_csv('tmp.csv').to_html('report_html.html')
    html=open('report_html.html').read()

    part1=MIMEText("Following are the instances currently running:\n","plain")
    part2=MIMEText(html,"html")
    message.attach(part1)
    message.attach(part2)

    context = ssl.create_default_context()
    with smtplib.SMTP(smtp_server, port) as server:
        server.ehlo() # Can be omitted
        server.starttls(context=context)
        server.ehlo() # Can be omitted
        server.login(sender_email,password)
        server.sendmail(sender_email, receiver_email, 
        message.as_string())

My separate try with part 1 and part2 output are given below:

Solution

You are using the wrong kind of multipart container. A multipart/alternative container tells the receiving client "here are multiple variants of the same content; display whichever one suits the user's preferences and your technical capabilities." But you want to say "here are several parts; display all of them, one way or another." A suitable content type for that is multipart/mixed or possibly multipart/related instead.