fixed significant bugs and added new features:

- resolved error on startup
- Youtube-dl is now the fallback downloader in case yt-dlp fails. Files are cleared when switching. 
- A failed download no longer raises an exception, but an error message is still shown and the execution will still fail.

DownYouNow.ipynb

@@ -1,5 +1,15 @@
 {
   "cells": [
+    {
+      "cell_type": "markdown",
+      "metadata": {
+        "id": "view-in-github",
+        "colab_type": "text"
+      },
+      "source": [
+        "<a href=\"https://colab.research.google.com/github/buzz-lightsnack-2007/DownYouNow/blob/development/DownYouNow.ipynb\" target=\"_parent\"><img src=\"https://colab.research.google.com/assets/colab-badge.svg\" alt=\"Open In Colab\"/></a>"
+      ]
+    },
     {
       "cell_type": "markdown",
       "metadata": {
@@ -10,7 +20,7 @@
         "\n",
         "**A 100% free YouTube video downloader.** \n",
         "\n",
-        "_Powered by `yt_dlp` and `youtube_dl`._"
+        "_Powered by [`YouTube-DL`](https://urlzs.com/AqDFN) and [`yt_dlp`](https://urlzs.com/rkBHD). ._"
       ]
     },
     {
@@ -70,6 +80,10 @@
         "    try: from google.colab import files\n",
         "    except: raise TypeError(\"No! Please run this in \" + formatting.font.bold + 'Google CoLab' + formatting.clear + '. ')\n",
         "\n",
+        "def fail(message = ''): \n",
+        "    # When the program fails, run this. \n",
+        "    clear(); info.title(); info.err(message); os.kill(os.getpid, 1);\n",
+        "\n",
         "def getExtension(fileName): \n",
         "    import os\n",
         "    fileName_split = os.path.splitext(fileName)\n",
@@ -81,7 +95,6 @@
         "def install(what, where = 'apt', isCritical = False):\n",
         "    os.system('add-apt-repository ppa:apt-fast/stable -y && apt-get update')\n",
         "\n",
-        "    info.status('Installing ' + what + '…')\n",
         "    try:\n",
         "        if (where == 'apt' or where == 'apt-get' or where == 'apt-fast' or where == 'aptitude'):\n",
         "            if os.system('DEBIAN_FRONTEND=noninteractive apt-fast install ' + what + ' -y'): \n",
@@ -93,11 +106,10 @@
         "            if os.system('DEBIAN_FRONTEND=noninteractive ' + where + ' install ' + what): raise\n",
         "    except:\n",
         "        errorMsg = (what + ' could not get installed. ')\n",
-        "        if isCritical: clear(); info.title(); raise SystemError('Critical component ' + errorMsg)\n",
+        "        if isCritical: fail('Critical component ' + errorMsg)\n",
         "        else: info.err(errorMsg); return True\n",
         "    else: \n",
         "        if os.system('apt-fast clean && apt-fast autoremove -y') > 0: os.system('apt clean && apt autoremove -y') > 0\n",
-        "        info.success('Installed '+ what + '.'); return False\n",
         "\n",
         "def install_required(): \n",
         "    def check_installDone(method='check'): \n",
@@ -105,23 +117,36 @@
         "        else: return not(os.system('cat .config/installDone'))\n",
         "\n",
         "    if not(check_installDone()): \n",
-        "        for program in ['apt-fast', 'yt-dlp', 'youtube-dl', 'libboost-all-dev']: \n",
+        "        # Install programs here using apt.\n",
+        "        for program in ['apt-fast', 'youtube-dl', 'libboost-all-dev']: \n",
         "            clear()\n",
         "            info.title(); info.status('Please wait.')\n",
         "            install(program)\n",
         "            clear()\n",
+        "        # install programs here using pip\n",
+        "        for program in ['yt-dlp']: \n",
+        "            info.title(); info.status('Please wait.')\n",
+        "            install(program, 'pip')\n",
+        "            clear()\n",
+        "        \n",
+        "        check_installDone('write')\n",
         "\n",
         "def save_video(): \n",
+        "\n",
         "    import google;\n",
         "\n",
         "    try:\n",
         "        info.title() \n",
         "        if not(user.audio_only):\n",
-        "            if os.system('yt-dlp \"' + user.video_link + '\" --compat-options no-youtube-unavailable-videos --merge-output-format ' + user.video_format + ' --audio-format ' + user.audio_format): raise\n",
+        "            if os.system('yt-dlp \"' + user.video_link + '\" --compat-options no-youtube-unavailable-videos --merge-output-format ' + user.video_format + ' --audio-format ' + user.audio_format): \n",
+        "                cleanup()\n",
+        "                if os.system('youtube-dl \"' + user.video_link + '\" --compat-options no-youtube-unavailable-videos --merge-output-format ' + user.video_format + ' --audio-format ' + user.audio_format): raise\n",
         "        else: \n",
-        "            if os.system('yt-dlp -x \"' + user.video_link + '\" --compat-options no-youtube-unavailable-videos --audio-format ' + user.audio_format): raise\n",
+        "            if os.system('yt-dlp -x \"' + user.video_link + '\" --compat-options no-youtube-unavailable-videos --audio-format ' + user.audio_format): \n",
+        "                cleanup()\n",
+        "                if os.system('youtube-dl -x \"' + user.video_link + '\" --compat-options no-youtube-unavailable-videos --audio-format ' + user.audio_format): raise\n",
         "    except: \n",
-        "        clear(); info.title(); raise UnboundLocalError(formatting.font.bold + 'The YouTube video could not be downloaded. ' + formatting.clear + 'Please try again. ')\n",
+        "        clear(); fail(formatting.font.bold + 'The YouTube video could not be downloaded. ' + formatting.clear + 'Please try again. ')\n",
         "    else: \n",
         "        info.success('Video cached. ')\n",
         "\n",
@@ -157,11 +182,14 @@
         "    audio_only = 0 #@param {type:\"slider\", min:0, max:1, step:1}\n",
         "\n",
         "    if not(audio_only): \n",
-        "        video_format = \"mp4\" #@param [\"mp4\", \"mkv\", \"webm\"]\n",
+        "        video_format = \"mkv\" #@param [\"mkv\", \"webm\"]\n",
         "    else: \n",
         "        video_format = False\n",
         "    \n",
-        "    audio_format = 'm4a' #@param ['mp3', 'm4a', 'wav']\n",
+        "    audio_format = 'm4a' #@param ['m4a']\n",
+        "\n",
+        "\n",
+        "install_required()\n",
         "\n",
         "try: \n",
         "    import yt_dlp;\n",
@@ -182,7 +210,6 @@
         "            video_title = info_dict.get('title', None)\n",
         "            output_format = '';\n",
         "\n",
-        "install_required()\n",
         "save_video()\n",
         "download_video()"
       ]
@@ -193,7 +220,8 @@
       "collapsed_sections": [],
       "name": "Untitled0.ipynb",
       "private_outputs": true,
-      "provenance": []
+      "provenance": [],
+      "include_colab_link": true
     },
     "kernelspec": {
       "display_name": "Python 3",