ah la ca semble bien

Flask/templates/proxy.html

@@ -53,7 +53,8 @@
         <tr>
             <td class="comlumn-name"></td>
             <td>
-                <select name="select" onchange="data = JSON.parse('{{data|tojson}}'); change_proxy(this.value, data)">
+                <script>data = JSON.parse('{{data|tojson}}');</script>
+                <select name="select" onchange="change_proxy(this.value, data)">
                     <option selected id="new" value="{{ len }}">Create new proxy</option>
                     {% for i in data %}
                     <option id="{{data[i]['name']}}" value="{{i}}">{{data[i]['name']}}</option>