The Overflow Blog. Who owns this outage? Building intelligent escalation chains for modern SRE. Podcast Who is building clouds for the independent developer? Featured on Meta. Now live: A fully responsive profile. Reducing the weight of our footer. Linked 0. Related Hot Network Questions. 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. After setting the maximum file size of the file in our python program, if we upload a file having a size of more than 1 Mb, then we will get the error as shown in the below image. While building a file uploader using Flask, we can also configure the file extensions that we want to upload.
To configure the allowed file extensions, we need to create a list of allowed extensions and check the uploaded file extension in the list. The below code shows a practical illustration of the method. In the above code, we create a function that will check the uploaded file extension and compare it with the allowed extensions. Till now, we have seen how to upload a single file to our server. But sometimes, we also want to upload multiple files to the server.
See the below code for illustration. After creating the Html form, we need to make some changes to our Flask application file. First, copy the following Python code into your Flask app file.
In the above code, we use python for loop to iterate over the list of files and then save each file one by one. We can choose multiple files now and upload them at once to the server. We have seen how to upload files using Flask, but sometimes we also want to serve a file to the user. First, create an HTML template in the templates folder, named the file download. Now, we need to create our app. In our app. Then, copy and paste the following code in the app.
After copying the above code, run the code by typing the command python app. If everything works fine and the server starts without any problem, we have created our file downloader. If you click the download button present in the URL, then the file will start downloading. For the above code to work properly, we need a file with the name sample.
In this tutorial, we learned to create a file uploader and file downloader using the Flask library. In addition, we have seen how to configure the max size and extension of the file upload. You may also want to see our step-by-step guide on creating a Flask app in python.
We can add more extension types in allowed extensions set for supporting different type of file uploads. It returns the index. Uploaded file attached in the POST request can be referenced by request. We check the name of the uploaded file before we save it to server filesystem.
This is done because there is a possibility that user might name the file which clashes with some system configuration file, In this case if uploaded filename is not changed then system file will be overwritten.
This vulnerability can be used by hackers to hack the server. For this task i. The reason could be, you want to generate reports from database and download these reports. Now I will create the web application that will download any kind of file which is kept in a server location.
First step is to create a project root directory under which I will put all the required files for the project. Create the below app. This file should be created under the project root directory. Notice how I create flask instance. 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.
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