question:# Asynchronous TCP Server-Client Model Objective Design and implement an asynchronous TCP server-client model using the asyncio package. Description You are required to implement two components: an asynchronous TCP server and an asynchronous TCP client. The server will receive messages from the client and respond by echoing the message back transformed to upper case. The client will send a predefined message to the server and print the response received from the server. Requirements **Server Implementation** 1. Create an asynchronous TCP server that listens on `localhost` at port `8888`. 2. The server should handle multiple client connections concurrently. 3. When a client sends a message to the server, the server should transform it to upper case and send it back to the client. 4. Close the connection gracefully after sending the response. **Client Implementation** 1. Create an asynchronous TCP client that connects to the server at `localhost` on port `8888`. 2. The client should send a predefined message to the server and wait for the server's response. 3. Print the response received from the server. 4. Close the connection gracefully after receiving the response. Function Signatures ```python async def start_server(): # Start the server and handle incoming connections async def handle_client(reader: asyncio.StreamReader, writer: asyncio.StreamWriter): # Handle individual client connection async def start_client(message: str): # Connect to the server, send a message, and receive the response ``` Input and Output **Server:** - No input - Output should be displayed in the console, showing connections and messages processed **Client:** - Input: A predefined string message - Output: The server's response to the predefined message Constraints - Use the asyncio package for asynchronous operations. - Ensure that the server can handle multiple clients concurrently without blocking. - Ensure proper exception handling for network operations. Example ```python # Run the server await start_server() # Run the client await start_client("hello world") # Console Output (Server Side): # Connection from ('127.0.0.1', 12345) # Received: hello world # Sent: HELLO WORLD # Connection closed # Console Output (Client Side): # Received: HELLO WORLD ``` Notes - The provided example shows how the server and client interact and the expected console outputs. - Ensure to test the implementation to demonstrate the server handling multiple clients concurrently.

question:# Question: You are required to implement a custom cookie handling mechanism using the `http.cookiejar` module in Python. The goal is to create a cookie manager that can: 1. Load cookies from a file. 2. Add a new cookie following specific rules. 3. Retrieve cookies based on a specific policy. 4. Save the modified cookies back to the file. Here's the detailed breakdown of the requirements: 1. **Loading Cookies**: - Implement a function `load_cookies(filename: str) -> http.cookiejar.MozillaCookieJar` that loads cookies from a given file into a `MozillaCookieJar` object. 2. **Adding/Modifying Cookies**: - Implement a function `add_cookie(cj: http.cookiejar.MozillaCookieJar, name: str, value: str, domain: str) -> None` that adds a new cookie or updates an existing cookie with the given name, value, and domain to the `MozillaCookieJar` object. - Ensure that the cookie has a secure attribute set to `True` and a path attribute set to `/`. 3. **Retrieve Cookies**: - Implement a function `get_cookies(cj: http.cookiejar.MozillaCookieJar, domain: str) -> list` that retrieves all cookies for the specified domain and returns a list of (name, value) tuples. 4. **Saving Cookies**: - Implement a function `save_cookies(cj: http.cookiejar.MozillaCookieJar, filename: str) -> None` that saves the cookies present in the `MozillaCookieJar` object to the specified file. # Constraints: - You must use the `http.cookiejar` module classes and not any other cookie management libraries. - The file format for saving and loading cookies should be compatible with the Mozilla cookies.txt format. - Ensure that all cookies added programmatically have their `secure` attribute set to `True`. # Example Usage: ```python # Initialize the CookieJar cookie_jar = load_cookies('cookies.txt') # Add a new cookie add_cookie(cookie_jar, 'sessionid', 'abcd1234', '.example.com') # Retrieve cookies for a specific domain cookies = get_cookies(cookie_jar, '.example.com') print(cookies) # Save cookies back to file save_cookies(cookie_jar, 'cookies.txt') ``` # Expected Input and Output: - `load_cookies(filename: str) -> http.cookiejar.MozillaCookieJar` - **Input**: 'cookies.txt' - **Output**: MozillaCookieJar object loaded with cookies from the file. - `add_cookie(cj: http.cookiejar.MozillaCookieJar, name: str, value: str, domain: str) -> None` - **Input**: MozillaCookieJar object, 'sessionid', 'abcd1234', '.example.com' - **Output**: None (cookie should be added to the MozillaCookieJar object) - `get_cookies(cj: http.cookiejar.MozillaCookieJar, domain: str) -> list` - **Input**: MozillaCookieJar object, '.example.com' - **Output**: List of cookies for the domain in the format [('name', 'value')] - `save_cookies(cj: http.cookiejar.MozillaCookieJar, filename: str) -> None` - **Input**: MozillaCookieJar object, 'new_cookies.txt' - **Output**: None (cookies should be saved in the file) Implement these functions to manage HTTP cookies efficiently and ensure the correct handling as per the requirement.

question:<|Analysis Begin|> The provided documentation describes the `cmd` module in Python, which provides a framework for building line-oriented command interpreters. This module is useful for creating custom shells that allow users to interact with a program through commands. Key Features: 1. **Cmd Class**: The `Cmd` class enables the creation of a command-line interface by inheriting its methods and defining custom commands using methods prefixed with `do_`. 2. **Methods**: - `cmdloop()`: Starts the command interpreter loop. - `onecmd()`: Processes a single command. - `emptyline()`, `default()`, `precmd()`, `postcmd()`, `preloop()`, `postloop()`: Hook methods for handling specific events in the command processing workflow. - `completedefault()`: Method for command completion. 3. **Instance Variables**: - `prompt`: The prompt string. - `intro`: Introductory text shown at the start of `cmdloop()`. - `cmdqueue`: Queue of commands to be executed. - `use_rawinput`, `identchars`, `lastcmd`, etc. The Cmd class aims to simplify writing interpreters by wrapping the boilerplate around handling input, help commands, and command execution flow. Based on this understanding, we can design a coding question that involves creating a custom command interpreter using the `cmd` module. <|Analysis End|> <|Question Begin|> # Custom Command Interpreter for a Simple File System You are tasked with creating a custom command-line interpreter for managing a simple file system of a single directory. This interpreter will allow users to create, read, and delete files. The files will only store text content. Implement a class `FileSystemShell` that inherits from `cmd.Cmd`. This class should provide the following commands: 1. **create <filename> <content>** - Description: Create a new file with the given filename and content. If a file with the same name already exists, it should display an error message. - Example: `create example.txt "Hello, World!"` 2. **read <filename>** - Description: Read and display the content of the specified file. If the file does not exist, it should display an error message. - Example: `read example.txt` 3. **delete <filename>** - Description: Delete the specified file. If the file does not exist, it should display an error message. - Example: `delete example.txt` 4. **list** - Description: List all files in the directory. - Example: `list` 5. **exit** - Description: Exit the command interpreter. - Example: `exit` You should also provide appropriate help messages for each command using docstrings. Here's a skeleton of the class to get you started: ```python import cmd class FileSystemShell(cmd.Cmd): intro = 'Welcome to the simple file system shell. Type help or ? to list commands.n' prompt = '(filesystem) ' files = {} def do_create(self, arg): 'Create a new file with the given filename and content: CREATE <filename> <content>' args = arg.split(maxsplit=1) if len(args) < 2: print("Error: Missing filename or content.") return filename, content = args if filename in self.files: print(f"Error: File '{filename}' already exists.") else: self.files[filename] = content print(f"File '{filename}' created.") def do_read(self, arg): 'Read the content of the specified file: READ <filename>' filename = arg.strip() if filename in self.files: print(self.files[filename]) else: print(f"Error: File '{filename}' not found.") def do_delete(self, arg): 'Delete the specified file: DELETE <filename>' filename = arg.strip() if filename in self.files: del self.files[filename] print(f"File '{filename}' deleted.") else: print(f"Error: File '{filename}' not found.") def do_list(self, arg): 'List all files in the directory: LIST' if self.files: for filename in self.files: print(filename) else: print("No files found.") def do_exit(self, arg): 'Exit the command shell: EXIT' print('Exiting the simple file system shell.') return True if __name__ == '__main__': FileSystemShell().cmdloop() ``` # Constraints: - Filenames must not contain spaces. - Content can be any string. # Input and Output Your program should run in an interactive mode similar to a command shell, accepting commands from the user and providing appropriate responses based on the command. Ensure you handle edge cases such as missing arguments or invalid command formats gracefully. # Performance Requirements: - The command interpreter should handle typical use cases efficiently. - Implement the command operations with optimal time complexity (e.g., O(1) for reading and writing to the file dictionary). Good luck!

question:# Custom Interactive Python Console **Objective**: Implement a customized interactive Python console using the `code` module, including special handling for certain user-defined commands and enhanced error management. # Requirements: 1. **Class Definition**: Define a class `CustomConsole` that inherits from `code.InteractiveConsole`. 2. **Custom Commands**: - Implement a command `#help` to print a custom help message. - Implement a command `#exit` to exit the console with a custom exit message. 3. **Enhanced Error Handling**: - Override the `showsyntaxerror` method to include the line number where the error occurred. - Override the `showtraceback` method to include the type of error that occurred. # Implementation Details: 1. **Class Initialization**: - The class should take an optional dictionary `locals` and an optional string `filename`. 2. **push(line)**: - Override the `push` method to handle the specific custom commands `#help` and `#exit`. 3. **write(data)**: - Override the `write` method to print error messages in a custom format. 4. **showsyntaxerror(filename=None)**: - Override to display syntax errors with the line number. 5. **showtraceback()**: - Override to display the type of error along with the standard traceback. # Constraints: - The `#help` command should print: "Custom Console Help: Type your Python code to execute it. Type #exit to exit." - The `#exit` command should print: "Exiting Custom Console..." before terminating the interactive session. - The custom error formatting should be clear and informative for users. # Input/Output: - **Input**: Python code lines and commands entered by the user in the interactive console. - **Output**: Execution results, custom help message, exit message, and enhanced error messages displayed in the console. # Example Usage: ```python >>> console = CustomConsole() >>> console.interact(banner="Welcome to the Custom Interactive Python Console!", exitmsg="Goodbye!") Welcome to the Custom Interactive Python Console! >>> print("Hello, World!") Hello, World! >>> #help Custom Console Help: Type your Python code to execute it. Type #exit to exit. >>> #exit Exiting Custom Console... Goodbye! ``` **Remember**: Your implementation should focus on creating a user-friendly and informative interactive console experience enhanced with custom commands and error handling.