Cómo agregar CSS en la aplicación Flask
<link rel= "stylesheet" type= "text/css" href= "{{ url_for('static',filename='styles/mainpage.css') }}">
Smoggy Sloth
<link rel= "stylesheet" type= "text/css" href= "{{ url_for('static',filename='styles/mainpage.css') }}">
<link rel="stylesheet" href="{{ url_for('static', filename='css/main.css') }}">{% block styles %}
{{super()}}
<link rel="stylesheet"
href="{{url_for('.static', filename='mystyle.css')}}">
{% endblock %}