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_posts/2025-01-29-fixing-the-osmwidget-in-django-admin.md

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+---
+layout: post
+title: Fixing the OSMWidget in Django Admin
+tags: [django, programming, python]
+---
+
+I was setting up an admin for some [Django](https://www.djangoproject.com/) models that had a PointField the other day, and I ran into an issue that took a little digging to figure out.
+
+Here's how I initially set up the admin, setting the `gis_widget_kwargs` like the [OSMWidget](https://docs.djangoproject.com/en/5.1/ref/contrib/gis/forms-api/#django.contrib.gis.forms.widgets.OSMWidget) documentation says:
+
+```python
+@admin.register(AddressModel)
+class AddressModelAdmin(GISModelAdmin):
+    gis_widget_kwargs = {
+        "default_lon": -85.3148324,
+        "default_lat": 40.3374484,
+        "default_zoom": 20,
+    }
+```
+
+But when I loaded the admin page for a given object of the model, I got the following error:
+
+```
+TypeError: OSMWidget.__init__() got an unexpected keyword argument 'default_lon'
+```
+
+Diggin into [the source code for OSMWidget](https://github.com/django/django/blob/main/django/contrib/gis/forms/widgets.py#L110) I noticed that the `__init__` function takes a keyword argument `attrs` which itself is a dict (or something that [getattr](https://docs.python.org/3/library/functions.html#getattr) can be used):
+
+```python
+class OSMWidget(OpenLayersWidget):
+    """
+    An OpenLayers/OpenStreetMap-based widget.
+    """
+
+    template_name = "gis/openlayers-osm.html"
+    default_lon = 5
+    default_lat = 47
+    default_zoom = 12
+
+    def __init__(self, attrs=None):
+        super().__init__()
+        for key in ("default_lon", "default_lat", "default_zoom"):
+            self.attrs[key] = getattr(self, key)
+        if attrs:
+            self.attrs.update(attrs)
+```
+
+So I had to modify my `gis_widget_kwargs` to be a single-value dict with a value that itself is the dict I previously thought I had to use:
+
+```python
+@admin.register(AddressModel)
+class AddressModelAdmin(GISModelAdmin):
+    gis_widget_kwargs = {
+        'attrs': {
+            "default_lon": -85.3148324,
+            "default_lat": 40.3374484,
+            "default_zoom": 20,
+        }
+    }
+```
+
+After this change, my admin page loaded correctly.