Avoid relying on .__iter__ to tell iterators apart

.send_file() would fail with stream objects (those from open())
since they are iterable, and asserting that they weren't bytes
or str was not enough.

telethon/events/__init__.py

@@ -14,7 +14,7 @@ def _into_id_set(client, chats):
     if chats is None:
         return None
 
-    if not hasattr(chats, '__iter__') or isinstance(chats, str):
+    if not utils.is_list_like(chats):
         chats = (chats,)
 
     result = set()

telethon/session.py

@@ -355,14 +355,14 @@ class Session:
         if not self.save_entities:
             return
 
-        if not isinstance(tlo, TLObject) and hasattr(tlo, '__iter__'):
+        if not isinstance(tlo, TLObject) and utils.is_list_like(tlo):
             # This may be a list of users already for instance
             entities = tlo
         else:
             entities = []
-            if hasattr(tlo, 'chats') and hasattr(tlo.chats, '__iter__'):
+            if hasattr(tlo, 'chats') and utils.is_list_like(tlo.chats):
                 entities.extend(tlo.chats)
-            if hasattr(tlo, 'users') and hasattr(tlo.users, '__iter__'):
+            if hasattr(tlo, 'users') and utils.is_list_like(tlo.users):
                 entities.extend(tlo.users)
             if not entities:
                 return

telethon/telegram_client.py

@@ -975,7 +975,7 @@ class TelegramClient(TelegramBareClient):
         """
         if max_id is None:
             if message:
-                if hasattr(message, '__iter__'):
+                if utils.is_list_like(message):
                     max_id = max(msg.id for msg in message)
                 else:
                     max_id = message.id
@@ -1140,7 +1140,7 @@ class TelegramClient(TelegramBareClient):
         """
         # First check if the user passed an iterable, in which case
         # we may want to send as an album if all are photo files.
-        if hasattr(file, '__iter__') and not isinstance(file, (str, bytes)):
+        if utils.is_list_like(file):
             # Convert to tuple so we can iterate several times
             file = tuple(x for x in file)
             if all(utils.is_image(x) for x in file):
@@ -1960,7 +1960,7 @@ class TelegramClient(TelegramBareClient):
             ``User``, ``Chat`` or ``Channel`` corresponding to the input
             entity.
         """
-        if hasattr(entity, '__iter__') and not isinstance(entity, str):
+        if utils.is_list_like(entity):
             single = False
         else:
             single = True

telethon/utils.py

@@ -5,6 +5,7 @@ to convert between an entity like an User, Chat, etc. into its Input version)
 import math
 import mimetypes
 import re
+import types
 from mimetypes import add_type, guess_extension
 
 from .tl.types import (
@@ -341,6 +342,17 @@ def is_video(file):
             (mimetypes.guess_type(file)[0] or '').startswith('video/'))
 
 
+def is_list_like(obj):
+    """
+    Returns True if the given object looks like a list.
+
+    Checking if hasattr(obj, '__iter__') and ignoring str/bytes is not
+    enough. Things like open() are also iterable (and probably many
+    other things), so just support the commonly known list-like objects.
+    """
+    return isinstance(obj, (list, tuple, set, dict, types.GeneratorType))
+
+
 def parse_phone(phone):
     """Parses the given phone, or returns None if it's invalid"""
     if isinstance(phone, int):