doc(book): data transfer to Python

book/src/SUMMARY.md

@@ -22,6 +22,8 @@
   - [Metadata processing with Python](./metadata_python.md)
   - [Advanced topics](./metadata_advanced.md)
 
+* [Data transfer to Python](./python.md)
+
 * [Error handling](./error_handling.md)
 
 * [Example programs](./examples.md)

book/src/python.md

@@ -0,0 +1,7 @@
+# Data transfer to Python
+
+The most straightforward method is to write data to a file.
+To do so, call `TableCollction::dump` or `TreeSequence::dump` as appropriate.
+
+It is also possible to transfer data to a Python tree sequence without making a copy.
+At the time of this writing, an experimental repository to do so is [here](https://github.com/molpopgen/tskit2tskit).