Fallback to MemorySession if sqlite3 is not available

telethon/client/telegrambaseclient.py

@@ -13,7 +13,7 @@ from ..crypto import rsa
 from ..extensions import markdown
 from ..network import MTProtoSender, ConnectionTcpFull
 from ..network.mtprotostate import MTProtoState
-from ..sessions import Session, SQLiteSession
+from ..sessions import Session, SQLiteSession, MemorySession
 from ..tl import TLObject, functions, types
 from ..tl.alltlobjects import LAYER
 
@@ -171,7 +171,18 @@ class TelegramBaseClient(abc.ABC):
 
         # Determine what session object we have
         if isinstance(session, str) or session is None:
+            try:
                 session = SQLiteSession(session)
+            except ValueError:
+                import warnings
+                warnings.warn(
+                    'The sqlite3 module is not available under this '
+                    'Python installation and no custom session '
+                    'instance was given; using MemorySession.\n'
+                    'You will need to re-login every time unless '
+                    'you use another session storage'
+                )
+                session = MemorySession()
         elif not isinstance(session, Session):
             raise TypeError(
                 'The given session must be a str or a Session instance.'

telethon/sessions/sqlite.py

@@ -1,7 +1,6 @@
 import datetime
 import json
 import os
-import sqlite3
 from base64 import b64decode
 from os.path import isfile as file_exists
 
@@ -13,6 +12,11 @@ from ..tl.types import (
     InputPhoto, InputDocument, PeerUser, PeerChat, PeerChannel
 )
 
+try:
+    import sqlite3
+except ImportError:
+    sqlite3 = None
+
 EXTENSION = '.session'
 CURRENT_VERSION = 4  # database version
 
@@ -27,6 +31,9 @@ class SQLiteSession(MemorySession):
     """
 
     def __init__(self, session_id=None):
+        if sqlite3 is None:
+            raise ValueError('sqlite3 is not installed')
+
         super().__init__()
         self.filename = ':memory:'
         self.save_entities = True