Send email with Siganture via Gmail API, Python - python-3.x

Question

I'm trying to send an email via the Gmail API using Python, I want to iclude the signature. I'm able to successfuly get the signature using the following funciotn:
def addSignature(service):
sigtanture = service.users().settings().sendAs().get(userId=USER, sendAsEmail='example#example.com').execute()
return sigtanture['signature']
addSignature(SERVICE)
However, at the time of creating the message that I'll send, how do I append the Signature?
def CreateMessage(sender, to, subject, message_text, signature):
message = MIMEMultipart('alternative')
message['to'] = to
message['from'] = sender
message['subject'] = subject
message[???] = signature
raw = base64.urlsafe_b64encode(message.as_bytes())
raw = raw.decode()
body = {'raw': raw}
return body
I'm trying to send the message:
thebody = CreateMessage(USER, 'to#example.com', 'TestSignatureAPI','testing', addSignature(SERVICE))
SendMessage(SERVICE, USER, thebody)
Thank you!

Answer 1

Unfortunately there is no built-in feature to append the Gmail signature to your email
Instead, once you retrieve your signature as a text, you can simply append it manually to the end of your message_text before encoding.
See also here.
Assuming you retrieved the signature correctly and based on your code this means:
def CreateMessage(sender, to, subject, message_text, signature):
message_text = message_text + "\n" + signature
message = MIMEMultipart('alternative')
message['to'] = to
message['from'] = sender
message['subject'] = subject
message.attach(MIMEText(message_text_plain, 'plain'))
raw = base64.urlsafe_b64encode(message.as_bytes())
raw = raw.decode()
body = {'raw': raw}
return body