prompt: We are currently solving the following issue within our repository. Here is the issue text:
  --- BEGIN ISSUE ---
  nltk.chat.chatbot() endless loop
  When I type `import nltk` followed by `nltk.chat.chatbots()`, it lists/asks which one I want to talk to, and then endlessly scrolls the following: ` Enter a number in the range 1-5:     Error: bad chatbot number`, in both Jupyter and Spyder.
  
  --- END ISSUE ---
  
  Below are some code segments, each from a relevant file. One or more of these files may contain bugs.
  --- BEGIN FILES ---
  Path: `nltk/chat/__init__.py`
  Content:
  ```
  1 # Natural Language Toolkit: Chatbots
  2 #
  3 # Copyright (C) 2001-2022 NLTK Project
  4 # Authors: Steven Bird <stevenbird1@gmail.com>
  5 # URL: <https://www.nltk.org/>
  6 # For license information, see LICENSE.TXT
  7 
  8 # Based on an Eliza implementation by Joe Strout <joe@strout.net>,
  9 # Jeff Epler <jepler@inetnebr.com> and Jez Higgins <jez@jezuk.co.uk>.
  10 
  11 """
  12 A class for simple chatbots.  These perform simple pattern matching on sentences
  13 typed by users, and respond with automatically generated sentences.
  14 
  15 These chatbots may not work using the windows command line or the
  16 windows IDLE GUI.
  17 """
  18 
  19 from nltk.chat.eliza import eliza_chat
  20 from nltk.chat.iesha import iesha_chat
  21 from nltk.chat.rude import rude_chat
  22 from nltk.chat.suntsu import suntsu_chat
  23 from nltk.chat.util import Chat
  24 from nltk.chat.zen import zen_chat
  25 
  26 bots = [
  27     (eliza_chat, "Eliza (psycho-babble)"),
  28     (iesha_chat, "Iesha (teen anime junky)"),
  29     (rude_chat, "Rude (abusive bot)"),
  30     (suntsu_chat, "Suntsu (Chinese sayings)"),
  31     (zen_chat, "Zen (gems of wisdom)"),
  32 ]
  33 
  34 
  35 def chatbots():
  36     import sys
  37 
  38     print("Which chatbot would you like to talk to?")
  39     botcount = len(bots)
  40     for i in range(botcount):
  41         print("  %d: %s" % (i + 1, bots[i][1]))
  42     while True:
  43         print("\nEnter a number in the range 1-%d: " % botcount, end=" ")
  44         choice = sys.stdin.readline().strip()
  45         if choice.isdigit() and (int(choice) - 1) in range(botcount):
  46             break
  47         else:
  48             print("   Error: bad chatbot number")
  49 
  50     chatbot = bots[int(choice) - 1][0]
  51     chatbot()
  52
  ```
  --- END FILES ---
  
  Please first localize the bug based on the issue statement, and then generate a patch according to the `git diff` format fenced by three backticks.
  
  Here is an example:
  
  ```diff
  diff --git a/examples/server_async.py b/examples/server_async.py
  --- a/examples/server_async.py
  +++ b/examples/server_async.py
  @@ -313,4 +313,4 @@
   
   
   if __name__ == "__main__":
  -    asyncio.run(run_async_server("."), debug=True)
  +    asyncio.run(run_async_server(), debug=True)
  diff --git a/examples/server_sync.py b/examples/server_sync.py
  --- a/examples/server_sync.py
  +++ b/examples/server_sync.py
  @@ -313,5 +313,5 @@
   
   
   if __name__ == "__main__":
  -    server = run_sync_server(".")
  +    server = run_sync_server()
       server.shutdown()
  
  ```
  
golden_diff: diff --git a/nltk/chat/__init__.py b/nltk/chat/__init__.py
  --- a/nltk/chat/__init__.py
  +++ b/nltk/chat/__init__.py
  @@ -33,15 +33,12 @@
   
   
   def chatbots():
  -    import sys
  -
       print("Which chatbot would you like to talk to?")
       botcount = len(bots)
       for i in range(botcount):
           print("  %d: %s" % (i + 1, bots[i][1]))
       while True:
  -        print("\nEnter a number in the range 1-%d: " % botcount, end=" ")
  -        choice = sys.stdin.readline().strip()
  +        choice = input(f"\nEnter a number in the range 1-{botcount}: ").strip()
           if choice.isdigit() and (int(choice) - 1) in range(botcount):
               break
           else:
  
verification_info: {"golden_diff": "diff --git a/nltk/chat/__init__.py b/nltk/chat/__init__.py\n--- a/nltk/chat/__init__.py\n+++ b/nltk/chat/__init__.py\n@@ -33,15 +33,12 @@\n \n \n def chatbots():\n-    import sys\n-\n     print(\"Which chatbot would you like to talk to?\")\n     botcount = len(bots)\n     for i in range(botcount):\n         print(\"  %d: %s\" % (i + 1, bots[i][1]))\n     while True:\n-        print(\"\\nEnter a number in the range 1-%d: \" % botcount, end=\" \")\n-        choice = sys.stdin.readline().strip()\n+        choice = input(f\"\\nEnter a number in the range 1-{botcount}: \").strip()\n         if choice.isdigit() and (int(choice) - 1) in range(botcount):\n             break\n         else:\n", "issue": "nltk.chat.chatbot() endless loop\nWhen I type `import nltk` followed by `nltk.chat.chatbots()`, it lists/asks which one I want to talk to, and then endlessly scrolls the following: ` Enter a number in the range 1-5:     Error: bad chatbot number`, in both Jupyter and Spyder.\n", "before_files": [{"content": "# Natural Language Toolkit: Chatbots\n#\n# Copyright (C) 2001-2022 NLTK Project\n# Authors: Steven Bird <stevenbird1@gmail.com>\n# URL: <https://www.nltk.org/>\n# For license information, see LICENSE.TXT\n\n# Based on an Eliza implementation by Joe Strout <joe@strout.net>,\n# Jeff Epler <jepler@inetnebr.com> and Jez Higgins <jez@jezuk.co.uk>.\n\n\"\"\"\nA class for simple chatbots.  These perform simple pattern matching on sentences\ntyped by users, and respond with automatically generated sentences.\n\nThese chatbots may not work using the windows command line or the\nwindows IDLE GUI.\n\"\"\"\n\nfrom nltk.chat.eliza import eliza_chat\nfrom nltk.chat.iesha import iesha_chat\nfrom nltk.chat.rude import rude_chat\nfrom nltk.chat.suntsu import suntsu_chat\nfrom nltk.chat.util import Chat\nfrom nltk.chat.zen import zen_chat\n\nbots = [\n    (eliza_chat, \"Eliza (psycho-babble)\"),\n    (iesha_chat, \"Iesha (teen anime junky)\"),\n    (rude_chat, \"Rude (abusive bot)\"),\n    (suntsu_chat, \"Suntsu (Chinese sayings)\"),\n    (zen_chat, \"Zen (gems of wisdom)\"),\n]\n\n\ndef chatbots():\n    import sys\n\n    print(\"Which chatbot would you like to talk to?\")\n    botcount = len(bots)\n    for i in range(botcount):\n        print(\"  %d: %s\" % (i + 1, bots[i][1]))\n    while True:\n        print(\"\\nEnter a number in the range 1-%d: \" % botcount, end=\" \")\n        choice = sys.stdin.readline().strip()\n        if choice.isdigit() and (int(choice) - 1) in range(botcount):\n            break\n        else:\n            print(\"   Error: bad chatbot number\")\n\n    chatbot = bots[int(choice) - 1][0]\n    chatbot()\n", "path": "nltk/chat/__init__.py"}], "after_files": [{"content": "# Natural Language Toolkit: Chatbots\n#\n# Copyright (C) 2001-2022 NLTK Project\n# Authors: Steven Bird <stevenbird1@gmail.com>\n# URL: <https://www.nltk.org/>\n# For license information, see LICENSE.TXT\n\n# Based on an Eliza implementation by Joe Strout <joe@strout.net>,\n# Jeff Epler <jepler@inetnebr.com> and Jez Higgins <jez@jezuk.co.uk>.\n\n\"\"\"\nA class for simple chatbots.  These perform simple pattern matching on sentences\ntyped by users, and respond with automatically generated sentences.\n\nThese chatbots may not work using the windows command line or the\nwindows IDLE GUI.\n\"\"\"\n\nfrom nltk.chat.eliza import eliza_chat\nfrom nltk.chat.iesha import iesha_chat\nfrom nltk.chat.rude import rude_chat\nfrom nltk.chat.suntsu import suntsu_chat\nfrom nltk.chat.util import Chat\nfrom nltk.chat.zen import zen_chat\n\nbots = [\n    (eliza_chat, \"Eliza (psycho-babble)\"),\n    (iesha_chat, \"Iesha (teen anime junky)\"),\n    (rude_chat, \"Rude (abusive bot)\"),\n    (suntsu_chat, \"Suntsu (Chinese sayings)\"),\n    (zen_chat, \"Zen (gems of wisdom)\"),\n]\n\n\ndef chatbots():\n    print(\"Which chatbot would you like to talk to?\")\n    botcount = len(bots)\n    for i in range(botcount):\n        print(\"  %d: %s\" % (i + 1, bots[i][1]))\n    while True:\n        choice = input(f\"\\nEnter a number in the range 1-{botcount}: \").strip()\n        if choice.isdigit() and (int(choice) - 1) in range(botcount):\n            break\n        else:\n            print(\"   Error: bad chatbot number\")\n\n    chatbot = bots[int(choice) - 1][0]\n    chatbot()\n", "path": "nltk/chat/__init__.py"}]}