Update examples to make them easier to run

telethon_examples/print_updates.py

@@ -1,18 +1,28 @@
 #!/usr/bin/env python3
 # A simple script to print all updates received
-#
-# NOTE: To run this script you MUST have 'TG_API_ID' and 'TG_API_HASH' in
-#       your environment variables. This is a good way to use these private
-#       values. See https://superuser.com/q/284342.
-from os import environ
+import os
+import sys
+import time
 
 from telethon import TelegramClient
 
 
+def get_env(name, message, cast=str):
+    if name in os.environ:
+        return os.environ[name]
+    while True:
+        value = input(message)
+        try:
+            return cast(value)
+        except ValueError as e:
+            print(e, file=sys.stderr)
+            time.sleep(1)
+
+
 client = TelegramClient(
-    environ.get('TG_SESSION', 'session'),
-    environ['TG_API_ID'],
-    environ['TG_API_HASH'],
+    os.environ.get('TG_SESSION', 'printer'),
+    get_env('TG_API_ID', 'Enter your API ID: ', int),
+    get_env('TG_API_HASH', 'Enter your API hash: '),
     proxy=None
 )