Flask â File Uploading
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Handling file upload in Flask is very easy. It needs an HTML form with its enctype attribute set to âmultipart/form-dataâ, posting the file to a URL. The URL handler fetches file from request.files[] object and saves it to the desired location.
Each uploaded file is first saved in a temporary location on the server, before it is actually saved to its ultimate location. Name of destination file can be hard-coded or can be obtained from filename property of request.files[file] object. However, it is recommended to obtain a secure version of it using the secure_filename() function.
It is possible to define the path of default upload folder and maximum size of uploaded file in configuration settings of Flask object.
| app.config[âUPLOAD_FOLDERâ] | Defines path for upload folder |
| app.config[âMAX_CONTENT_PATHâ] | Specifies maximum size of file yo be uploaded â in bytes |
The following code has â/uploadâ URL rule that displays âupload.htmlâ from the templates folder, and â/upload-fileâ URL rule that calls uploader() function handling upload process.
âupload.htmlâ has a file chooser button and a submit button.
<html>
<body>
<form action = "http://localhost:5000/uploader" method = "POST"
enctype = "multipart/form-data">
<input type = "file" name = "file" />
<input type = "submit"/>
</form>
</body>
</html>
You will see the screen as shown below.
Click Submit after choosing file. Formâs post method invokes â/upload_fileâ URL. The underlying function uploader() does the save operation.
Following is the Python code of Flask application.
from flask import Flask, render_template, request
from werkzeug import secure_filename
app = Flask(__name__)
@app.route(''/upload'')
def upload_file():
return render_template(''upload.html'')
@app.route(''/uploader'', methods = [''GET'', ''POST''])
def upload_file():
if request.method == ''POST'':
f = request.files[''file'']
f.save(secure_filename(f.filename))
return ''file uploaded successfully''
if __name__ == ''__main__'':
app.run(debug = True)
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