更新：
在新版本的Telethon中，@ Lonami答案是最好的并使用它。
client = TelegramClient('session_name',
api_id,
api_hash,
update_workers=1,
spawn_read_thread=False)
assert client.connect()
if not client.is_user_authorized():
client.send_code_request(phone_number)
me = client.sign_in(phone_number, input('Enter code: '))
channel_username='tehrandb' # your channel
channel_entity=client.get_entity(channel_username)
posts = client(GetHistoryRequest(
peer=channel_entity,
limit=100,
offset_date=None,
offset_id=0,
max_id=0,
min_id=0,
add_offset=0,
hash=0))
# messages stored in `posts.messages`
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