How to show more options in flask wtforms multiple select?

Issue

I am using flask wtforms multiple select that is showing 4 options by default and as I have the sth like 20 options in total, scrolling isn't really convenient. Is there a way to make the select higher to show more than 4 options at a time?

I tried to use rows attribute, but probably I did it wrong as it is not working(I don't know too much about HTML)

Part of my code related to this:

class PositionForm(FlaskForm):
    position = SelectMultipleField(u'Choose position:')
...

@app.route('/custom', methods=['POST', 'GET'])
def custom():
    position_form.position.choices = []
    for position in positions_db:
        positions.append(position.name)
        position_form.position.choices.append((position.name, position.name))
...
    return render_template('table.html',... , position_form=position_form)

HTML code:

<form action="/custom" method="post" style="margin: 2px 10px 2px 10px; font-weight: bold;">
    <div>{{ position_form.position.label }}<br>
    {{ position_form.position(rows=6, multiple=True) }}</div>
</form>

Solution

You can just add size attribute when calling the form, example:

<div>{{ position_form.position.label }}<br>
{{ position_form.position(rows=6, multiple=True, size=15) }}</div>

Answered By - Yago de Carvalho Souto