Download file as attachment flask python

As we haven't set a variable rule, Flask will default to string and not allow any slashes. If you try a filename that doesn't exist, you'll get a Not Found error in your browser.

You'll notice these 2 routes are very similar to the first, with the addition of the filename variable. Both router are identical apart from the addition of their corresponding file extensions in the filename variable, where we've just used an f string to append the extension to the filename. We've hard coded the extension this way as we're only allowing that type of file extension from their given route. You could of course omit it and ask the user to provide the file extension too.

You may want a nested directory structure within your trusted base directory, where users can provide a path to a file in the URL to retrieve a file. Let's say reports is our trusted base directory, containing several sub-directories and files, like so:.

Without using a database, we can create a dynamic system of URL's and allow users to provide a path to a file. Let's create a new route and put this into practice, allowing our user to download a report by providing a path in the URL. We're doing exactly the same as above, with the exception of adding the path prefix to the URL variable.

The path should be relative from the reports directory saved in our app. Likewise any non-existent filenames would throw a error. The reason? Instead, a micro-framework Flask is very powerful and is highly extensible.

In this tutorial, we will learn how to create a file uploader and file downloader using Flask. File Uploading and downloading is an important task for a website.

For example, assume that we were building a site that takes some images from user uploads and converts them into a single PDF. We need to learn to upload and download files using server-side frameworks like Flask in such a scenario. We can install Flask easily with the help of the pip tool.

PIP is a command-line tool, and it is the default package manager for managing python packages. To install the Flask framework, we need to run the following command in the terminal. On running the above command in the terminal, we will have Flask installed in our system.

We can check our installation by opening the python shell and importing the Flask library. See the below image for illustration.

The first step while creating our file uploader is to build the Html form. First, create a templates folder in the current directory. After that, create a file with the name upload. After creating the HTML template for the file uploader, now, in the main directory, create a file with the name app.

The app. Copy the following code into the app. In the above code, we first imported the required modules to our code. After importing the required modules, we initialize the Flask app by calling the Flask constructor.

Next, we use python decorators to define the routes for our Flask app and serve the HTML template that we created. Next, we use python decorators to accept the post request for the file and save the file. You can run the above code by just typing python app. We will see something as shown in the below image while running the above code. Upload a sample file by choosing a file and clicking the submit button.

After submitting the file, we will get a message showing that the file has been successfully uploaded. We can check the file in the server by visiting the root directory. We created a file uploader that saves the uploaded file in the root directory.

We can also configure the directory for saving the file by configuring the app. At first, the uploaded file is saved into a temporary location, and then it moves to the final location. The following code shows how to configure the upload directory. In the above code, we use the OS module of python to create a directory and saves every uploaded file to the created directory.

If we restart the server and upload a file to the server, the file will be uploaded to the created directory instead of the root directory. We can also configure the maximum upload size of the file. This is important because if the file is too large for the server, then the site may crash. So, we need to always limit the upload size of the file according to our server. To configure the maximum file size, we need to set the app.

For example, if we want to limit the maximum size of the file to 1 Mb, we need to add the following line of code in our program. Next I will create main. In the above source code, the root path or endpoint will simply render the UI. This UI contains only one link for downloading a file from the server. Clicking on the link will ask user to save the file in a chosen location. The file type could be anything. As you see I have tested with four types of files.

I hope this example will work with other file types as well. Now create a download. Notice in the above template file I am using Flask EL Expression language to evaluate the link endpoint. Now navigate to the project root directory from command line tool and execute the command python main.

If you want to change the port then you can change the line app. Any way to clear the cache from Flask?