Can open file for async access

The next example is similar to the previous one but uses StreamReader and StreamWriter objects to read and write the contents of a text file asynchronously. The next example shows the code-behind file and the XAML file that are used to open a file as a Stream in a Windows 8.

It uses asynchronous methods to open the file as a stream and to read its contents. Skip to main content. This browser is no longer supported. Download Microsoft Edge More info. You can break out the portion of your code that handles each file into its own async function, and append promises for those function calls to a list of tasks.

Here's an example of what that function, and your new main function would look like:. This is a common way to utilize asynchronous code in Python, and is often used for things like making HTTP requests. The examples in this post using data from the Pokemon were just an excuse to show the functionality of the aiofiles module, and how you would write code to navigate through a directory of files for reading and writing.

We have only scratched the surface of what you can do with aiohttp and asyncio, but I hope that this has made starting your journey into the world of asynchronous Python a little easier. Feel free to reach out and share your experiences or ask any questions. We are always striving to improve our blog quality, and your feedback is valuable to us. How could this post serve you better?

Download Now. Log In Sign Up Close. Use Cases. Support Plans Status. Build the future of communications. Sample applications that cover common use cases in a variety of languages. Download, test drive, and tweak them yourself. Let's move on and dig deeper. If each FileStream was instead created in a using statement, the FileStream might be disposed of before the task was complete.

Any performance boost is almost entirely from the parallel processing and not the asynchronous processing. The advantages of asynchrony are that it doesn't tie up multiple threads, and that it doesn't tie up the user interface thread. When using the xref:System. CancellationToken, which you can use to cancel the operation mid-stream. For more information, see Cancellation in managed threads. Skip to content. Star 3.

Permalink main. Branches Tags. Could not load branches. Could not load tags. Raw Blame. You can learn more about using app data locations from the guidance on the ApplicationData class page, and by downloading the Application data sample from GitHub. You can learn more about using app URIs in How to load file resources. Additionally, your app can access some of the files on connected devices by default. This is an option if your app uses the AutoPlay extension to launch automatically when users connect a device, like a camera or USB thumb drive, to their system.

The files your app can access are limited to specific file types that are specified via File Type Association declarations in your app manifest.

Of course, you can also gain access to files and folders on a removable device by calling the file picker using FileOpenPicker and FolderPicker and letting the user pick files and folders for your app to access. Learn how to use the file picker in Open files and folders with a picker. By default, your app can only access files and folders in the user's Downloads folder that your app created. However, you can gain access to files and folders in the user's Downloads folder by calling a file picker FileOpenPicker or FolderPicker so that users can navigate and pick files or folders for your app to access.

CreateFileAsync is overloaded so that you can specify what the system should do if there is already an existing file in the Downloads folder that has the same name. When these methods complete, they return a StorageFile that represents the file that was created. This file is called newFile in the example. CreateFolderAsync is overloaded so that you can specify what the system should do if there is already an existing subfolder in the Downloads folder that has the same name.

When these methods complete, they return a StorageFolder that represents the subfolder that was created. This file is called newFolder in the example. In addition to the default locations, an app can access additional files and folders by declaring capabilities in the app manifest or by calling a file picker to let the user pick files and folders for the app to access. Apps that declare the AppExecutionAlias extension have file-system permissions from the directory that they are launched from in the console window, and downwards.

When your app retrieves a file or folder via a picker, a file activation, a drag-and-drop operation, etc.