---
title: Tech Stack
category: stack
---

# Tech Stack

## Runtime & Language
- **Python >=3.13**

## Web Framework
- **Streamlit** - Multi-page app with Home, Stemwijzer, Explorer pages

## Data Layer
- **DuckDB** - Embedded OLAP database
  - Tables: motions, mp_votes, svd_vectors, fused_embeddings, embeddings, user_sessions, party_results, mp_metadata
- **ibis** - ORM (referenced but DuckDB-native implementation used)

## AI / LLM
- **OpenRouter** - API abstraction for AI providers
- **QWEN** - Primary model
  - Embeddings: `qwen/qwen3-embedding-4b`
  - Chat: `qwen/qwen-2.5-72b-instruct`
- **requests** - HTTP client (not raw openai)

## ML / Analytics
- **scikit-learn** - KMeans clustering, cosine_similarity, StandardScaler
- **scipy** - SVD (scipy.linalg.svd), spatial.procrustes
- **umap-learn** - Dimensionality reduction (optional, graceful fallback to SVD)
- **numpy** - Numerical computing

## Visualization
- **Plotly** - Interactive charts (go.Figure, _DummyTrace fallback)
- **matplotlib** - Static plotting (optional)

## HTTP & Parsing
- **requests** - Session pooling, retry with backoff
- **beautifulsoup4** - HTML parsing
- **lxml** - XML/HTML processing

## Key Source Files

| File | Purpose |
|------|---------|
| `database.py` | MotionDatabase singleton, DuckDB connection, 9-table schema |
| `explorer.py` | Explorer page with 4 tabs (Motion, MP, Party, Evolution) |
| `explorer_helpers.py` | Pure helper functions, Plotly chart builders |
| `analysis/` | SVD pipeline, UMAP projection, clustering |
| `pipeline/` | Data fetch, transform, store pipeline |
| `pages/1_Stemwijzer.py` | Quiz page |
| `pages/2_Explorer.py` | Explorer page |
| `config.py` | Dataclass Config pattern |
| `ai_provider.py` | OpenRouter API wrapper with retry |
| `api_client.py` | TweedeKamer OData API client |

## Singleton Instances

| Module | Instance | Type |
|--------|----------|------|
| `database.py` | `db` | `MotionDatabase` |
| `config.py` | `config` | `Config` (dataclass) |
| `config.py` | `PARTY_COLOURS` | `dict[str, str]` |

## Environment
- Python >=3.13
- Environment variables via `.env` (DB path, API keys)
- No `.env` values in constraint files (security)