A script to download all the media from the specified Telegram channel.

channel_download.py

import os, sys
from telethon import TelegramClient, sync
import asyncio

# These example values won't work. You must get your own api_id and
# api_hash from https://my.telegram.org, under API Development.
API_ID = 12345
API_HASH = '0123456789abcdef0123456789abcdef'

count = 0
len_queue_full = 0
client = None
msgs = []

def download_chat(client, channel_name, root_dir, limit):
	channel_dir = os.path.join(root_dir, channel_name)
	try:
		os.makedirs(channel_dir)
	except FileExistsError:
		pass
	os.chdir(channel_dir)
	if limit == -1:
		msgs = client.get_messages(channel_name, limit = 99999)
	else:
		msgs = client.get_messages(channel_name, limit = limit)
	
	return msgs
	
		
async def crawl_worker(msg_id):
	global len_queue_full, msgs
	try:
		file_name = "%d.jpg" % msg_id
		if (not os.path.exists(file_name)) or os.stat(file_name).st_size == 0:
			await msgs[msg_id].download_media(file = file_name)
		
	except:
		return

	print("[%d / %d] %s" % (msg_id + 1, len_queue_full, file_name))

async def coro(start, num_threads = 5):
	global len_queue_full
	#print(len_queue_full)
	tasks = [asyncio.ensure_future(crawl_worker(i)) for i in range(start, start + num_threads)]
	await asyncio.wait(tasks)

def main(channel_name, root_dir = "G:/telegram", limit = -1, start = 0):
	global len_queue_full, count, client, msgs
	if not client:
		client = TelegramClient('session_name', API_ID, API_HASH)
		client.start()

	print("getting messages from %s" % channel_name)
	msgs = download_chat(client, channel_name, root_dir, limit)[::-1]
	len_queue_full = len(msgs)
	print("ready")
	try:
		import cryptg
		num_threads = 50
	except:
		num_threads = 8
	
	ioloop = asyncio.get_event_loop()
	while start < len_queue_full:
		ioloop.run_until_complete(coro(start, num_threads))
		start += num_threads
	#ioloop.close()