docs: add Python API reference page

CHANGELOG.md

@@ -6,6 +6,12 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added
+
+- Docs: Python API reference page (`python-api`) covering `openqbw.open`,
+  `Reader`, and its `tables()` / `indexes()` / `line_items()` /
+  `transactions()` methods, registered in the sidebar. Fixes #1. (@Nabejo)
+
 ## [0.1.4] - 2026-07-06
 
 ### Changed

docs/docs/python-api.md

@@ -0,0 +1,77 @@
+# Python API reference
+
+The `openqbw` wheel is a PyO3 extension built from the same Rust core
+that backs the CLI. It exposes a small, read-only surface: open a file,
+then pull the catalog, indexes, line items, and transaction headers as
+lists of dicts.
+
+```python
+import openqbw
+
+r = openqbw.open("/path/to/file.qbw")
+print(r.page_count, "pages,", r.file_size, "bytes")
+```
+
+## `openqbw.open(path) -> Reader`
+
+Opens a `.qbw` file, decodes the page store, and learns the additive
+progression model needed to attribute pages to tables. Raises
+`OSError` if the file cannot be opened.
+
+## `Reader`
+
+| Member | Type | Description |
+|---|---|---|
+| `path` | `str` | The filesystem path the reader was opened from. |
+| `page_count` | `int` | Number of pages in the underlying page-store. |
+| `file_size` | `int` | File size in bytes. |
+| `tables()` | `list[dict]` | SYSTABLE catalog rows. |
+| `indexes()` | `list[dict]` | SYSINDEX entries. |
+| `line_items()` | `list[dict]` | Invoice line items, attributed to their source table. |
+| `transactions()` | `list[dict]` | Transaction headers. |
+
+### `tables()`
+
+Each dict has `table_id`, `name`, `col_count`, `data_root_page`,
+`last_page`, `page_number`.
+
+```python
+for t in r.tables()[:5]:
+    print(t["table_id"], t["name"])
+```
+
+### `indexes()`
+
+Each dict has `name`, `table_id`, `root_page`, `page_number`.
+
+```python
+for idx in r.indexes()[:5]:
+    print(idx["name"], idx["table_id"])
+```
+
+### `line_items()`
+
+Each dict has `invoice_id`, `item_qb_id`, `amount_cents`,
+`amount_cents_signed`, `txn_date_days_since_unix`, `source_table`,
+`page_number`, `page_offset`.
+
+```python
+for li in r.line_items()[:3]:
+    print(li["invoice_id"], li["amount_cents"], li["source_table"])
+```
+
+### `transactions()`
+
+Each dict has `qb_id`, `source_table`, `txn_type`, `page_number`,
+`page_offset`.
+
+```python
+for h in r.transactions()[:3]:
+    print(h["qb_id"], h["txn_type"])
+```
+
+## Next
+
+- [Python quickstart](./quickstart-python)
+- [CLI reference](./cli)
+- [Format specification](./specification)

docs/sidebars.ts

@@ -21,6 +21,7 @@ const sidebars: SidebarsConfig = {
                 'use-cases',
                 'migration-guide',
                 'cli',
+                'python-api',
             ],
         },
         {