如何在没有访问令牌或重定向的情况下使用GMAIL API发送带有附件的消息

import os
import base64
from googleapiclient.discovery import build
from google.oauth2 import service_account
from email.mime.text import MIMEText
from email.mime.multipart import MIMEMultipart
from email.mime.base import MIMEBase
from email import encoders

# 服务账号的JSON密钥文件路径
credentials_file = 'path/to/credentials.json'

# 创建服务账号凭据
credentials = service_account.Credentials.from_service_account_file(
    credentials_file, scopes=['https://www.googleapis.com/auth/gmail.compose'])

# 创建Gmail API客户端实例
service = build('gmail', 'v1', credentials=credentials)

def create_message_with_attachment(sender, to, subject, message_text, file_path):
    message = MIMEMultipart()
    message['to'] = to
    message['from'] = sender
    message['subject'] = subject

    msg = MIMEText(message_text)
    message.attach(msg)

    # 添加附件
    attachment = MIMEBase('application', 'octet-stream')
    attachment.set_payload(open(file_path, 'rb').read())
    encoders.encode_base64(attachment)
    attachment.add_header('Content-Disposition', 'attachment', filename=os.path.basename(file_path))
    message.attach(attachment)

    return {'raw': base64.urlsafe_b64encode(message.as_bytes()).decode()}

def send_message(service, user_id, message):
    try:
        message = service.users().messages().send(userId=user_id, body=message).execute()
        print('Message sent. Message Id: %s' % message['id'])
        return message
    except Exception as e:
        print('An error occurred: %s' % e)
        return None

# 发送带有附件的消息
sender = 'your-email@gmail.com'
to = 'recipient@example.com'
subject = 'Test Email with Attachment'
message_text = 'This is a test email with attachment.'
attachment_file = 'path/to/attachment.pdf'

message = create_message_with_attachment(sender, to, subject, message_text, attachment_file)
send_message(service, 'me', message)