Python - Render Jinja template and Email

Question

I am testing this code, I got from Github, to render jinja template and send as an email.
When I run the code as below. I get the following error message. Need help to identify and resolve the issue. Thanks.

JayMac$ python3 "send_email.py"

ERROR:root:Error sending email
ERROR:root:object of type 'filter' has no len()
Traceback (most recent call last):
File "send_email.py", line 47, in send_email
server.sendmail(sender, to_list, msg.as_string())
File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/smtplib.py", line 878, in sendmail
if len(senderrs) == len(to_addrs):
TypeError: object of type 'filter' has no len()

Here is the code I am using -

*** send_email.py ****

import sys, os.path, logging 
from jinja2 import Environment, PackageLoader
from os import path 

def render_template(template, **kwargs): 
''' renders a Jinja template into HTML '''
# check if template exists
if not os.path.exists(template):
    print('No template file present: %s' % template)
    sys.exit()

import jinja2
templateLoader = jinja2.FileSystemLoader(searchpath="/")
templateEnv = jinja2.Environment(loader=templateLoader)
templ = templateEnv.get_template(template)
return templ.render(**kwargs)

#-----------------------------------------------------------

def send_email(to, sender='jk<jk@gmail.com>', cc=None, bcc=None, subject=None, body=None):
''' sends email using a Jinja HTML template '''

import smtplib
# Import the email modules
from email.mime.multipart import MIMEMultipart
from email.mime.text import MIMEText
from email.header import Header
from email.utils import formataddr
from email.mime.base import MIMEBase
from email import encoders

# convert TO into list if string
if type(to) is not list:
    to = to.split()

to_list = to + [cc] + [bcc]
to_list = filter(None, to_list) # remove null emails

msg = MIMEMultipart('alternative')
msg['From']    = sender
msg['Subject'] = subject
msg['To']      = ','.join(to)
msg['Cc']      = cc
msg['Bcc']     = bcc
msg.attach(MIMEText(body, 'html'))
server = smtplib.SMTP_SSL('smtp.gmail.com') # or your smtp server
try:
    server.login('jk@gmail.com', 'password')
    logging.info('sending email xxx')
    server.sendmail(sender, to_list, msg.as_string())

except Exception as e:
    logging.error('Error sending email')
    logging.exception(str(e))
finally:
    server.quit()

#-----------------------------------------------------------------------------------

# MAIN

item1 = 'kryptonite'
item2 = 'green clothing'

# generate HTML from template
html = render_template('default.j2', vars=locals())

to_list = ['xyz@gmail.com', 'vcb@gmail.com']
sender = 'jk<jk@gmail.com>'
cc = ''
bcc = ''
subject = 'Testing Jinja Email'

# send email to a list of email addresses
# send_email(to_list, sender, cc, bcc, subject, html.encode('utf-8'))
send_email(to_list, sender, cc, bcc, subject, html)

Answer 1

The error is in this line:

to_list = filter(None, to_list) # remove null emails 

it should be

to_list = list(filter(None, to_list) # remove null emails

because sendmail expects an actual list , not the iterator type returned by filter() .