Flask File Upload

Handling file uploads in Flask is very simple. It requires an enctype attribute set to 'multipart/form-HTML form with 'data', submit the form to the specified URL. The URL handler extracts the file from the request.files[] object and saves it to the required location.

Each uploaded file is first saved in a temporary location on the server and then saved to the final location. The target file name can be hardcoded or obtained from the filename attribute of the request.files [file] object. However, it is recommended to use the secure_filename() function to get its secure version.

You can define the default upload folder path and the maximum size of the uploaded file in the Flask object's configuration settings.

Variable	Description
app.config[‘UPLOAD_FOLDER’]	Define the path of the upload folder
app.config[‘MAX_CONTENT_PATH’]	Specify the maximum size of the file to be uploaded - in bytes

The following code has a URL: /upload rule, which displays the upload.html file in the templates folder, and the URL => calling the uploader() function to handle the upload process /upload-file rule.

upload.html has a file selector button and a submit button.

# Filename : example.py
# Copyright :　2020 By w3codebox
# Author by: www.oldtoolbag.com
# Date :　2020-08-08
<html>
　<head>
　<meta http-equiv="Content-Type" content="text/html; charset=utf-8"　/>
　<title>Flask Example</title>
　</head>
　　　　<body>
　　　　　　<form action="http://localhost:5000/upload" method="POST"　
　　　　　　　　　　enctype="multipart/form-data">
　　　　　　　　　　<input type="file" name="file"　/>
　　　　　　　　　　<input type="submit" value="Submit">/>
　　　　　　　</form>
　　　　</body>
　</html>

You will see the following screenshot as shown -

Click after selecting a file Submit. The post method of the form calls the URL=> /The underlying function uploader() in upload_file. performs the file saving operation.

The following is the Python code for the Flask application.

Example

# Filename : example.py
# Copyright :　2020 By w3codebox
# Author by: www.oldtoolbag.com
# Date :　2020-08-08
from flask import Flask, render_template, request
　from werkzeug import secure_filename
　app = Flask(__name__)
　@app.route('/upload', methods=['GET', 'POST'])
　def upload_file():
　　　　　if request.method == 'POST':
　　　　　　　　　f = request.files['file']
　　　　　　　　　print(request.files)
　　　　　　　　　f.save(secure_filename(f.filename))
　　　　　　　　　return 'file uploaded successfully'
　　　　　else:
　　　　　　　　　return render_template('upload.html')
　if __name__ == '__main__':
　　　　　app.run(debug=True)

After running the program, execute the code above, select an image file, and then click upload to get the following result -

Flask Extensions Flask Flash Messages

Flask Tutorial

Flask File Upload