Reader-Writer.ipynb

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      "\n",
      "\n",
      "Reader 0 is reading resource: \n",
      "Hello, Reader-writer problem here it is\n",
      "Helooo\n",
      "Reader 0 is reading resource: \n",
      "\n",
      "Thanks\n",
      "Reader 1 is reading resource: \n",
      "\n",
      "Thanks\n"
     ]
    }
   ],
   "source": [
    "import threading # Importing threading module for using semaphores\n",
    "import random\n",
    "import time\n",
    "\n",
    "# Shared resources\n",
    "readers_count = 0 # Number of readers reading the resource\n",
    "readers_count_lock = threading.Semaphore() # Semaphore for readers_count\n",
    "can_read = threading.Semaphore(0) # Semaphore for readers\n",
    "can_write = threading.Semaphore(1) # Semaphore for writers\n",
    "mutex = threading.Semaphore(1) # Semaphore for mutual exclusion\n",
    "\n",
    "\n",
    "NO_READERS = int(input(\"Enter the number of readers: \")) # Number of readers\n",
    "NO_WRITERS = int(input(\"Enter the number of writers: \")) # Number of writers\n",
    "\n",
    "\n",
    "# Reader function\n",
    "def reader(id): \n",
    "    global readers_count # Number of readers reading the resource\n",
    "    mutex.acquire() # Locking the mutex\n",
    "\n",
    "    readers_count_lock.acquire() # Locking the readers_count_lock\n",
    "    readers_count += 1 # Incrementing the number of readers\n",
    "    if readers_count == 1: # If the reader is the first reader\n",
    "        can_write.acquire() # Locking the can_write semaphore\n",
    "    readers_count_lock.release() # Releasing the readers_count_lock\n",
    "\n",
    "    mutex.release() # Releasing the mutex\n",
    "    can_read.release() # Releasing the can_read semaphore\n",
    "    resource = open(\"text.txt\", \"r\") # Opening the resource\n",
    "    content = resource.read() # Reading the resource\n",
    "    resource.close() # Closing the resource\n",
    "    \n",
    "    print(f\"Reader {id} is reading resource: \\n{content}\") # Printing the content of the resource\n",
    "    can_read.acquire() \n",
    "    \n",
    "    readers_count_lock.acquire()\n",
    "    readers_count -= 1 # Decrementing the number of readers\n",
    "    if readers_count == 0: # If the reader is the last reader\n",
    "        can_write.release() # Releasing the can_write semaphore\n",
    "    readers_count_lock.release()\n",
    "\n",
    "# Writer function\n",
    "def writer(id):\n",
    "    time.sleep(random.random()) # Random sleep time\n",
    "    can_write.acquire() # Locking the can_write semaphore\n",
    "    mode = input(\"Enter the mode of writing:\\na) append(a)\\nb) write(w): \")\n",
    "    resource = open(\"text.txt\", mode) # Opening the resource\n",
    "    value = input(f\"Enter the text you want to append by writer {id}:\")\n",
    "    value = \"\\n\" + value # Appending a new line before the text\n",
    "    resource.write(value) # Writing the value to the resource\n",
    "    resource.close() # Closing the resource\n",
    "    can_read.release()\n",
    "    can_write.release()\n",
    "print(\"\\n\")\n",
    "reader0 = threading.Thread(target=reader, args=(0,))\n",
    "reader0.start()\n",
    "\n",
    "\n",
    "reader_list = [\"reader0\", ] # List of reader threads\n",
    "writer_list = [] # List of writer threads\n",
    "for i in range (1, NO_READERS): # Creating the list of reader threads\n",
    "    var = \"reader\" + str(i)\n",
    "    reader_list.append(var)\n",
    "\n",
    "for i in range (1, NO_WRITERS+1): \n",
    "    var = \"writer\" + str(i)\n",
    "    writer_list.append(var)\n",
    "\n",
    "# Starting Function Threads\n",
    "for i in writer_list:\n",
    "    i = threading.Thread(target=writer, args=(int(i[-1]),))\n",
    "    i.start()\n",
    "    i.join()\n",
    "    for j in reader_list:\n",
    "        j = threading.Thread(target=reader, args=(int(j[-1]),))\n",
    "        j.start()\n",
    "        j.join()"
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