tiles="OpenStreetMap" returned HTTP 403 "referer is required by tile usage policy" in the target browser — OSM graylists refererless requests and a karte.html opened via file:// sends no Referer. Esri's Canvas/World_Light_Gray base + reference layers need neither a key nor a Referer and keep the muted look. New MAP_TILES / MAP_TILES_LABELS / MAP_TILES_ATTR constants; generate_map adds them as explicit TileLayers. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
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Dev notes — assumptions that turned out wrong
Running list so the same mistakes aren't repeated. Add to it whenever reality contradicts an assumption.
The macOS system Python can't run the GUI; use a Homebrew Python (2026-09-07)
The macOS CommandLineTools Python 3.9 (/Library/Developer/CommandLineTools/ .../python3.9) ships Tk 8.5.9. ttkbootstrap 1.10.1 requires Tk 8.6+.
Symptoms: TclError: couldn't recognize image data (window icon) and
TclError: unknown option "-style" on ttk.Scrollbar.
Fix for local GUI testing: brew install python-tk@3.12 (pulls tcl-tk,
gives Python 3.12 + Tk 9.0), then:
/opt/homebrew/bin/python3.12 -m venv venv
venv/bin/pip install -r requirements.txt
venv/bin/python app.py
ttkbootstrap 1.10.1 runs fine on Tk 9.0 in practice (verified: window builds,
Treeview sort, DateEntry, LabelFrame, custom styles all work).
- The Linux Mint target uses its own
python3-tk(Tk 8.6+) and is unaffected either way. screencapturefrom a non-GUI shell fails ("could not create image from display") without Screen-Recording permission — automated screenshots of the running app aren't available here; verify by building the widget tree and driving it programmatically instead.
pandas reads everything as strings by design
DataStore._load uses dtype={...: str} for postal_code, lat, lon.
Numeric parsing is deliberately deferred to get_map_data (pd.to_numeric(..., errors="coerce")). Don't "fix" columns to float on load — blank coordinates and
leading-zero PLZ both depend on the string representation.
Map tiles: Carto needs a key, OSM 403s file:// — use Esri (2026-09-07)
Two dead ends before landing on Esri:
folium.Map(tiles="CartoDB positron")→ "API KEY REQUIRED" watermark; Carto moved basemaps behind a key.tiles="OpenStreetMap"→ worked incurlfrom the dev machine but the user's browser got HTTP 403 "referer is required by tile usage policy". OSM's tile CDN graylists refererless requests, and akarte.htmlopened as a localfile://sends noReferer. A browser can't add one. Dead end for this app's "open a local HTML file" model.
Now: Esri "World Light Gray" base + reference (labels) overlay
(server.arcgisonline.com/ArcGIS/rest/services/Canvas/…). No key, no Referer
check, light/muted look close to the old positron. MAP_TILES /
MAP_TILES_LABELS constants; comment lists Esri Street/Topo as swaps.
Lesson: a tile source that works from curl or an http:// page can still fail
from file://. Test the map by opening the generated karte.html directly,
not just by checking the URL in the HTML.
Nominatim query order matters
geocode_city returns the first hit, trying PLZ-qualified first, then each
region in GEOCODE_REGIONS, then a bare ", Germany". Reordering changes which
coordinates ambiguous town names resolve to.