fix: make pumpkin-py build without any additional installs

pumpkin-py/Cargo.toml

@@ -12,5 +12,5 @@ name = "pumpkin_py"
 crate-type = ["cdylib"]
 
 [dependencies]
-pyo3 = "0.23.0"
+pyo3 = { version = "0.23.3", features= ["extension-module"] }
 pumpkin-solver = { path = "../pumpkin-solver" }

pumpkin-py/README.md

@@ -22,5 +22,24 @@ again.
 
 Then, the examples (for example `nqueens`) can be run with 
 ```
-python python/examples/nqueens.py 5
+python examples/nqueens.py 5
 ```
+
+### PyO3 rebuilds
+
+When developing in an IDE that runs `cargo check` on save, the PyO3 build 
+cache can get invalidated unnecessarily. See https://github.com/PyO3/pyo3/issues/1708
+for more details. One way to fix this is by making `rust-analyzer` use a
+different directory. In VSCode, you could fix this by adding the following
+to your `.vscode/settings.json` (in the main project directory):
+
+```json
+{
+    "rust-analyzer.server.extraEnv": {
+        "CARGO_TARGET_DIR": "target/analyzer"
+    },
+    "rust-analyzer.check.extraArgs": [
+        "--target-dir=target/analyzer"
+    ]
+}
+```

pumpkin-py/examples/nqueens.py

@@ -26,7 +26,7 @@ def main(n: int, proof: Path | None):
             for row in range(n):
                 print(f"{row_separator}");
 
-                queen_col = solution.value(variables[row])
+                queen_col = solution.int_value(variables[row])
 
                 for col in range(n): 
                     string = "| * " if queen_col == col else "|   "