route.py

@app.route("/upload", methods=["GET", "POST"])
def upload_file():
    form = FileUploadForm()
    if form.validate_on_submit():
        file = form.document.data
        file_name = secure_filename(file.filename)
        save_path = get_user_uploads_folder(current_user) / file_name
        file.save(save_path)
        flash("File uploaded successfully", category="success")
        return redirect(url_for("list_user_files"))
    flash_form_errors(form)
    return render_template("upload_file.html", form=form)