Nested env (#3159)

* Environment names for complex types #2304

* nested env disabled by default

* cleanup

* nested env settings: simplified and mypy fixes

* nested env settings: config, test, doc

* nested env settings: changes file

* nested env settings: cleanup

* Apply suggestions from code review

Co-authored-by: Samuel Colvin <samcolvin@gmail.com>

* Apply suggested changes from code review

* lint fix

* changes from code review

* simplify explosing env vars

* linting

Co-authored-by: Mark Trifonov <>
Co-authored-by: Samuel Colvin <samcolvin@gmail.com>
Co-authored-by: Samuel Colvin <s@muelcolvin.com>

docs/examples/settings_nested_env.py

@@ -0,0 +1,23 @@
+from pydantic import BaseModel, BaseSettings
+
+
+class DeepSubModel(BaseModel):
+    v4: str
+
+
+class SubModel(BaseModel):
+    v1: str
+    v2: bytes
+    v3: int
+    deep: DeepSubModel
+
+
+class Settings(BaseSettings):
+    v0: str
+    sub_model: SubModel
+
+    class Config:
+        env_nested_delimiter = '__'
+
+
+print(Settings().dict())