Add examples showcasing how to embed RustPython in Rust applications

cedric-h · cedric-h · commit 9beb44251d63 · 2020-01-26T00:42:35.000-05:00
diff --git a/README.md b/README.md
@@ -72,6 +72,13 @@ cargo build --release --target wasm32-wasi --features="freeze-stdlib"
 
 > Note: we use the `freeze-stdlib` to include the standard library inside the binary.
 
+
+## Embedding RustPython into your Rust Applications
+
+Interested in exposing Python scripting in an application written in Rust,
+perhaps to allow quickly tweaking logic where Rust's compile times would be inhibitive?
+Then `examples/hello_embed.rs` and `examples/mini_repl.rs` may be of some assistance.
+
 ## Disclaimer
 
 RustPython is in a development phase and should not be used in production or a
diff --git a/examples/hello_embed.rs b/examples/hello_embed.rs
@@ -0,0 +1,20 @@
+use rustpython_compiler::compile;
+use rustpython_vm::{pyobject::PyResult, PySettings, VirtualMachine};
+
+fn main() -> PyResult<()> {
+    let vm = VirtualMachine::new(PySettings::default());
+
+    let scope = vm.new_scope_with_builtins();
+
+    let code_obj = vm
+        .compile(
+            r#"print("Hello World!")"#,
+            compile::Mode::Exec,
+            "<embedded>".to_string(),
+        )
+        .map_err(|err| vm.new_syntax_error(&err))?;
+
+    vm.run_code_obj(code_obj, scope)?;
+
+    Ok(())
+}
diff --git a/examples/mini_repl.rs b/examples/mini_repl.rs
@@ -0,0 +1,53 @@
+///! This example show cases a very simple REPL.
+///! While a much better REPL can be found in ../src/shell,
+///! This much smaller REPL is still a useful example because it showcases inserting
+///! values and functions into the Python runtime's scope, and showcases use
+///! of the compilation mode "Single".
+///! Note that in particular this REPL does a horrible job of showing users their errors
+///! (instead it simply crashes).
+use rustpython_compiler::compile;
+use rustpython_vm::{pyobject::PyResult, PySettings, VirtualMachine};
+// this needs to be in scope in order to insert things into scope.globals
+use rustpython_vm::pyobject::ItemProtocol;
+
+fn main() -> PyResult<()> {
+    let mut on = true;
+
+    let mut input = String::with_capacity(50);
+    let stdin = std::io::stdin();
+
+    let vm = VirtualMachine::new(PySettings::default());
+    let scope = vm.new_scope_with_builtins();
+
+    // typing `quit()` is too long, let's make `on(False)` work instead.
+    scope
+        .globals
+        .set_item(
+            "on",
+            vm.context().new_rustfunc({
+                let on: *mut bool = &mut on;
+                move |b: bool, _: &VirtualMachine| unsafe { *on = b }
+            }),
+            &vm,
+        )
+        .unwrap();
+
+    while on {
+        input.clear();
+        stdin.read_line(&mut input).unwrap();
+
+        let code_obj = vm
+            .compile(&input, compile::Mode::Single, "<embedded>".to_string())
+            .map_err(|err| vm.new_syntax_error(&err))?;
+
+        // this line also automatically prints the output
+        let output = vm.run_code_obj(code_obj, scope.clone())?;
+
+        // store the last value in the "last" variable
+        if !vm.is_none(&output) {
+            scope.globals.set_item("last", output, &vm).unwrap();
+        }
+    }
+
+    Ok(())
+}
