From 88597f0da8ee348f0da2312c1f403b112c99b121 Mon Sep 17 00:00:00 2001
From: Lonami Exo <totufals@hotmail.com>
Date: Sat, 14 Apr 2018 12:08:50 +0200
Subject: [PATCH] Don't get full channel on iter_participants unless necessary

---
 telethon/telegram_client.py | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/telethon/telegram_client.py b/telethon/telegram_client.py
index 72b60e61..503f1c0f 100644
--- a/telethon/telegram_client.py
+++ b/telethon/telegram_client.py
@@ -1247,11 +1247,14 @@ class TelegramClient(TelegramBareClient):
 
         limit = float('inf') if limit is None else int(limit)
         if isinstance(entity, InputPeerChannel):
-            total = self(GetFullChannelRequest(
-                entity
-            )).full_chat.participants_count
-            if _total:
-                _total[0] = total
+            if _total or (aggressive and not filter):
+                total = self(GetFullChannelRequest(
+                    entity
+                )).full_chat.participants_count
+                if _total:
+                    _total[0] = total
+            else:
+                total = 0
 
             if limit == 0:
                 return