diff --git a/notebooks/uebung_regex.ipynb b/notebooks/uebung_regex.ipynb
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+{
+ "cells": [
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "# 12. Ãœbungsblatt\n",
+    "\n",
+    "Mit diesem Python-Code können Sie Ihren regulären Ausdruck testen:"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "import re\n",
+    "\n",
+    "\"\"\"\n",
+    "Ändern Sie den folgenden regulären Ausdruck, so dass alle \n",
+    "positiven Muster erkannt werden, aber kein negatives Muster.\n",
+    "\"\"\"\n",
+    "muster = re.compile(\" \") \n",
+    "positive = [\n",
+    "    \"rap them\",\n",
+    "    \"tapeth\",\n",
+    "    \"apth\",\n",
+    "    \"wrap/try\",\n",
+    "    \"sap tray\",\n",
+    "    \"87ap9th\",\n",
+    "    \"apothecary\"\n",
+    "]\n",
+    "\n",
+    "negative = [\n",
+    "    \"aleht\",\n",
+    "    \"happy them\",\n",
+    "    \"tarpth\",\n",
+    "    \"Apt\",\n",
+    "    \"peth\",\n",
+    "    \"tarreth\",\n",
+    "    \"ddapdg\",\n",
+    "    \"apples\",\n",
+    "    \"shape the\"\n",
+    "]\n",
+    "\n",
+    "# testen, ob alle positiven Muster richtig erkannt werden\n",
+    "positive_not_matched = [s for s in positive if not muster.findall(s)]\n",
+    "if positive_not_matched:\n",
+    "    print(\"Folgende positive Muster wurden nicht erkannt:\", \", \".join(positive_not_matched))\n",
+    "\n",
+    "# testen, ob keine negativen Muster erkannt werden\n",
+    "negative_matched = [s for s in negative if muster.findall(s)]\n",
+    "if negative_matched:\n",
+    "    print(\"Folgende negativen Muster wurden erkannt:\", \", \".join(negative_matched))\n"
+   ]
+  }
+ ],
+ "metadata": {
+  "language_info": {
+   "name": "python",
+   "pygments_lexer": "ipython3"
+  }
+ },
+ "nbformat": 4,
+ "nbformat_minor": 2
+}