# AWS Region-Specific Information Directory<html></html>---
> **This is a *developer preview* (public beta) module. Releases might lack important features and might have
> future breaking changes.**
>
> This API is still under active development and subject to non-backward
> compatible changes or removal in any future version. Use of the API is not recommended in production
> environments. Experimental APIs are not subject to the Semantic Versioning model.
---
<html></html>## Usage
Some information used in CDK Applications differs from one AWS region to
another, such as service principals used in IAM policies, S3 static website
endpoints, ...
### The `RegionInfo` class
The library offers a simple interface to obtain region specific information in
the form of the `RegionInfo` class. This is the preferred way to interact with
the regional information database:
```python
from aws_cdk.region_info import RegionInfo
# Get the information for "eu-west-1":
region = RegionInfo.get("eu-west-1")
# Access attributes:
region.s3_static_website_endpoint# s3-website.eu-west-1.amazonaws.com
region.service_principal("logs.amazonaws.com")
```
The `RegionInfo` layer is built on top of the Low-Level API, which is described
below and can be used to register additional data, including user-defined facts
that are not available through the `RegionInfo` interface.
### Low-Level API
This library offers a primitive database of such information so that CDK
constructs can easily access regional information. The `FactName` class provides
a list of known fact names, which can then be used with the `RegionInfo` to
retrieve a particular value:
```python
import aws_cdk.region_info as region_info
code_deploy_principal = region_info.Fact.find("us-east-1", region_info.FactName.service_principal("codedeploy.amazonaws.com"))
# => codedeploy.us-east-1.amazonaws.com
static_website = region_info.Fact.find("ap-northeast-1", region_info.FactName.S3_STATIC_WEBSITE_ENDPOINT)
```
## Supplying new or missing information
As new regions are released, it might happen that a particular fact you need is
missing from the library. In such cases, the `Fact.register` method can be used
to inject FactName into the database:
```python
region_info.Fact.register(
region="bermuda-triangle-1",
name=region_info.FactName.service_principal("s3.amazonaws.com"),
value="s3-website.bermuda-triangle-1.nowhere.com"
)
```
## Overriding incorrect information
In the event information provided by the library is incorrect, it can be
overridden using the same `Fact.register` method demonstrated above, simply
adding an extra boolean argument:
```python
# INCORRECT
region_info.Fact.register({
"region": "us-east-1",
"name": region_info.FactName.service_principal("service.amazonaws.com"),
"value": "the-correct-principal.amazonaws.com"
}, True)
```
If you happen to have stumbled upon incorrect data built into this library, it
is always a good idea to report your findings in a [GitHub issue](https://github.com/aws/aws-cdk/issues), so we can fix
it for everyone else!
---
This module is part of the [AWS Cloud Development Kit](https://github.com/aws/aws-cdk) project.