Catch error and display message using flash in Flask-CodePudding

I have a flask application where the user has to upload a file, then some operation happens on it and the result is displayed.

The restriction on file size is 2 MB. For this, I have used

app.config['MAX_CONTENT_LENGTH'] = 2 * 1000 * 1000

There is errorhandler function in flask to display custom error messages...

@app.errorhandler(413)
def page_not_found(e):
    return "File should be less than 2 MB"

But it is displayed on a new page.

I want the error to be displayed on the same page so that user can try with a new file. As it is now, to upload a new file the user has to press the back button to switch back to the previous page and then upload the file.

Is there a way to do this? Like, using 'flash' or something else?

CodePudding user response：

Using flash is possible. First, flash your message and then render the template.

@app.errorhandler(413)
def page_not_found(e):
    flash("File should be less than 2 MB")
    return render_template('myPage.html')

In your html, use Jinja:

{% with messages = get_flashed_messages() %}
            {% if messages %}
                <div class="popup">
                    <div class="text-center">
                        <script>window.alert('{{ messages[0] }}')</script>
                    </div>
                </div>
            {% endif %}
            {% endwith %}