FF-3392 feat(python): add Configuration.get_bandits_configuration (#50)

* FF-3392 feat(python): add Configuration.get_bandits_configuration

* chore(python): add `--no-index` do disable installing python-sdk from pypi

For CI, we should always install our SDK from dist. Without
`--no-index`, I found that pip randomly decides between local build
and pypi (unless we bumped the version locally), so CI would randomly
fail.

* chore(python): bump version

Author: rasendubi

.github/workflows/python.yml

@@ -82,7 +82,7 @@ jobs:
           set -ex
           python3 -m venv .venv
           source .venv/bin/activate
-          pip install eppo-server-sdk --find-links dist --force-reinstall
+          pip install eppo-server-sdk --no-index --find-links dist --force-reinstall
           pip install pytest cachetools
           npm ci
           npm run with-server test:python
@@ -99,7 +99,7 @@ jobs:
             pip3 install -U pip pytest cachetools
           run: |
             set -ex
-            pip3 install eppo-server-sdk --find-links dist --force-reinstall
+            pip3 install eppo-server-sdk --no-index --find-links dist --force-reinstall
             npm ci
             npm run with-server test:python
 
@@ -167,7 +167,7 @@ jobs:
             python3 -m virtualenv .venv
             source .venv/bin/activate
             pip install pytest cachetools
-            pip install eppo-server-sdk --find-links dist --force-reinstall
+            pip install eppo-server-sdk --no-index --find-links dist --force-reinstall
             npm ci
             npm run with-server test:python
 
@@ -206,7 +206,7 @@ jobs:
           set -ex
           python3 -m venv .venv
           source .venv/Scripts/activate
-          pip install eppo-server-sdk --find-links dist --force-reinstall
+          pip install eppo-server-sdk --no-index --find-links dist --force-reinstall
           pip install pytest cachetools
           npm ci
           npm run with-server test:python
@@ -243,7 +243,7 @@ jobs:
           set -ex
           python3 -m venv .venv
           source .venv/bin/activate
-          pip install eppo-server-sdk --find-links dist --force-reinstall
+          pip install eppo-server-sdk --no-index --find-links dist --force-reinstall
           pip install pytest cachetools
           npm ci
           npm run with-server test:python

python-sdk/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "eppo_py"
-version = "4.0.3"
+version = "4.1.0"
 edition = "2021"
 publish = false
 

python-sdk/python/eppo_client/_eppo_client.pyi

@@ -10,6 +10,7 @@ class Configuration:
         self, *, flags_configuration: bytes, bandits_configuration: bytes | None = None
     ) -> None: ...
     def get_flags_configuration(self) -> bytes: ...
+    def get_bandits_configuration(self) -> bytes | None: ...
     def get_flag_keys(self) -> Set[str]: ...
     def get_bandit_keys(self) -> Set[str]: ...
 

python-sdk/src/configuration.rs

@@ -2,7 +2,11 @@
 // backend to pass on configuration when initializing the frontend.
 use std::{borrow::Cow, sync::Arc};
 
-use pyo3::{exceptions::PyValueError, prelude::*, types::PySet};
+use pyo3::{
+    exceptions::{PyRuntimeError, PyValueError},
+    prelude::*,
+    types::PySet,
+};
 
 use eppo_core::{ufc::UniversalFlagConfig, Configuration as CoreConfiguration};
 
@@ -68,6 +72,23 @@ impl Configuration {
     fn get_flags_configuration(&self) -> Cow<[u8]> {
         Cow::Borrowed(self.configuration.flags.to_json())
     }
+
+    /// Return bytes representing bandits configuration.
+    ///
+    /// It should be treated as opaque and passed on to another Eppo client for initialization.
+    fn get_bandits_configuration(&self) -> PyResult<Option<Cow<[u8]>>> {
+        self.configuration
+            .bandits
+            .as_ref()
+            .map(|it| serde_json::to_vec(it).map(Cow::Owned))
+            .transpose()
+            .map_err(|err| {
+                // This should normally never happen.
+                PyRuntimeError::new_err(format!(
+                    "failed to serialize bandits configuration: {err:?}"
+                ))
+            })
+    }
 }
 
 impl Configuration {

python-sdk/tests/test_configuration.py

@@ -48,7 +48,6 @@
 BANDITS_MODEL_CONFIG = json.dumps(
     {
         "updatedAt": "2023-09-13T04:52:06.462Z",
-        "environment": {"name": "Test"},
         "bandits": {
             "car_bandit": {
                 "banditKey": "car_bandit",
@@ -116,6 +115,19 @@ def test_init_invalid_format(self):
                 flags_configuration=b'{"createdAt":"2024-09-09T10:18:15.988Z","environment":{"name":"test"},"flags":[]}'
             )
 
+    def test_get_bandits_configuration(self):
+        configuration = Configuration(
+            flags_configuration=FLAGS_CONFIG_WITH_BANDITS,
+            bandits_configuration=BANDITS_MODEL_CONFIG,
+        )
+
+        bandits_configuration = configuration.get_bandits_configuration()
+
+        # JSON parsing is an internal detail and is not a public
+        # guarantee. We're using it here because serialization order
+        # of bandits is not guaranteed.
+        assert json.loads(bandits_configuration) == json.loads(BANDITS_MODEL_CONFIG)
+
 
 @pytest.mark.rust_only
 def test_configuration_none():