复制此代码时，出现错误：

连接=无^ IndentationError：应缩进的块

然后，当我缩进代码时，

class FetchEmail():
    connection = None
    error = None
    mail_server = "imap.gmail.com"
    username = "dummyoffers@gmail.com"
    password = "opennepo"
    self.save_attachment(self, msg, download_folder)

我收到另一个错误：

self.save_attachment（self，msg，download_folder）NameError：未定义名称“ self”

import email
import imaplib
import os

class FetchEmail():

connection = None
error = None
mail_server="host_name"
username="outlook_username"
password="password"
self.save_attachment(self,msg,download_folder)
def __init__(self, mail_server, username, password):
    self.connection = imaplib.IMAP4_SSL(mail_server)
    self.connection.login(username, password)
    self.connection.select(readonly=False) # so we can mark mails as read

def close_connection(self):
    """
    Close the connection to the IMAP server
    """
    self.connection.close()

def save_attachment(self, msg, download_folder="/tmp"):
    """
    Given a message, save its attachments to the specified
    download folder (default is /tmp)

    return: file path to attachment
    """
    att_path = "No attachment found."
    for part in msg.walk():
        if part.get_content_maintype() == 'multipart':
            continue
        if part.get('Content-Disposition') is None:
            continue

        filename = part.get_filename()
        att_path = os.path.join(download_folder, filename)

        if not os.path.isfile(att_path):
            fp = open(att_path, 'wb')
            fp.write(part.get_payload(decode=True))
            fp.close()
    return att_path

def fetch_unread_messages(self):
    """
    Retrieve unread messages
    """
    emails = []
    (result, messages) = self.connection.search(None, 'UnSeen')
    if result == "OK":
        for message in messages[0].split(' '):
            try: 
                ret, data = self.connection.fetch(message,'(RFC822)')
            except:
                print "No new emails to read."
                self.close_connection()
                exit()

            msg = email.message_from_string(data[0][1])
            if isinstance(msg, str) == False:
                emails.append(msg)
            response, data = self.connection.store(message, '+FLAGS','\\Seen')

        return emails

    self.error = "Failed to retreive emails."
    return emails

上面的代码可以让我下载附件，希望对任何人都有帮助。