Pythonで複数の宛先にメールを送信する(Python3)

TO,CC,BCCに複数の宛先を指定するときハマったのでメモ
send_messageというメソッドはメッセージオブジェクトをそのまま引数にしてsendmail() を呼び出せると書いてあるので使ってみた。
大変便利だと思う。

#!/usr/bin/env python
# -*- coding: utf-8 -*-
import smtplib
from email.mime.multipart import MIMEMultipart
from email.mime.text      import MIMEText

def send_msg(
    from_addr, to_addrs = [], cc_addrs = [], bcc_addrs = [],
    subject = "", body_html = "", body_text = ""):
    msg  = MIMEMultipart('alternative')
    msg['Subject'] = subject
    msg['From']    = from_addr
    msg['To']      = ",".join(to_addrs)

    if cc_addrs !=[]:
        msg['Cc'] = ",".join(cc_addrs)
    if bcc_addrs !=[]:
        msg['Bcc'] = ",".join(bcc_addrs)

    cset = 'utf-8'

    if body_text != "":
        attachment_text = MIMEText(body_text, 'plain', cset)
        msg.attach(attachment_text)

    if body_html != "":
        attachment_html = MIMEText(body_html, 'html' , cset)
        msg.attach(attachment_html)

    smtp_con = smtplib.SMTP('localhost',25)
    smtp_con.set_debuglevel(True)
    smtp_con.send_message(msg = msg)
    smtp_con.close()