Building a REST API with AWS Gateway and Python
Tags: python, api, tutorial, webdev
Published: 2023-03-31 22:32:08

AWS Gateway is a powerful tool for building APIs that scale to meet the demands of modern web and mobile applications. With AWS Gateway, you can create RESTful APIs that expose your data and business logic to developers who can then build rich, interactive applications that consume your API.

REST API is an industry standard for building scalable, distributed web applications. With AWS Gateway, you can easily build a REST API that supports both `GET` and `POST` methods, as well as complex query parameters. You can also add support for other HTTP methods, such as `PUT`, `DELETE`, and `HEAD`.

Using AWS Gateway, you can quickly create APIs that are secure and robust. You can also use it to deploy your code to a production environment with minimal effort. Additionally, AWS Gateway allows for seamless integration with other AWS services, such as S3 and DynamoDB, enabling you to easily add complex functionality to your APIs.

## Prerequisites

Before building a RESTful API with AWS Gateway, you should have the following in place:

- [Create an AWS account](https://signin.aws.amazon.com/signin){:target="_blank" rel="noopener noreferrer"} if you don't have one already.

- Log in to the AWS Management Console and navigate to the Amazon API Gateway service.

![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/1fm2pbvrmlpp1yeep3hp.png)

- Click on "Create API" and select "REST API".

![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/fuf2m0h2t9nuzhtaq8p3.png)

![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/zh84k1tc21vjun4023hn.png)

- Click on "Actions" and define the resource and click "Create Resource".

![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/yvij76so0hh7tm13zcfl.png)

- Select the newly created resource and click on "Create Method".

![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/alxwjp2ppo8th3ys40e7.png)

![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/kic09omhogl0r5ei5epn.png)

- Choose the HTTP verb (e.g. GET, POST, PUT, etc.) and click on the checkmark to create the method.

- In the "Integration type" section, select "Lambda Function" and enter the name of the Lambda function you want to use to handle the API requests.
- Click on "Save" to create the API.

![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/wh99xljlxhafg963xhtp.png)

- Select Node from the Runtime Dropdown.

![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/0cq1w4z6jrhb5pwci2hk.png)

## Code Example

```javascript
let user = {
    firstName: "John",
    lastName: "Smith",
    location: "Bay Area"
}

export const handler = async(event) => {
    // TODO implement
    console.log(">>>> Inside Lambda Function....");
    if(event.httpMethod === "GET")
    {
        getUserRecord(event);
    }
    if(event.httpMethod === "POST")
    {
        createUserRecord(event)
    }

    const response = {
        statusCode: 200,
        body: JSON.stringify({
            user_details: user
        })
    };
    return response;
};

function getUserRecord (event) {

    const response = {
        statuscode: 200,
        body: JSON.stringify({
            user_details: user
        })
    };
    return response;
}

function createUserRecord(event) {
    const body = JSON.parse(event.body);
    const response = {
        statusCode: 200,
        body:JSON.stringify({
            message: "successfully created",
            details: body
        })
    };
    return response;
}
```

The code first creates an object called `user` that contains some properties like `firstName`, `lastName`, and `location`.

Then the handler function checks the httpMethod property of the event object, if it's "GET" it calls the `getUserRecord` function and if it's "POST" it calls the ``createUserRecord`` function.

Both `getUserRecord` and `createUserRecord` functions takes the `event` object as input and returns the `response` object.

In the `getUserRecord` function, it creates a `response` object with a `statusCode` of `200` and a body that contains a JSON object with `user_details` property which is the user object created at the beginning.

In the `createUserRecord` function, it first parse the `event.body` which is a string, into a JSON object and then creates a response object with a statusCode of `200` and a body that contains a JSON object with `message` and `details` properties.

Deploy the API by clicking on "Actions" and selecting "Deploy API".

![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/n4vxwigy5uhkuhu66g9m.png)

Select a deployment stage (e.g. "prod" or "test") and click on "Deploy".
Use the generated API endpoint to make requests to your API.

![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/6hlkywsjkm6lu9ktp5j9.png)

## Running and Testing The Code in Postman

Now, our API is up and running. You can send a test HTTP request through Postman. By sending a request to your `invoke URL`, you should see a `200 OK` status code. For this test, no request body is needed for the incoming request.

![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/my0m570csdu1f30i1obc.png)

## Wrapping Up

With that, we’ve created a simple RESTful API using AWS Lambda. This code can then be expanded on as needed to build APIs for your applications. Moving forward, you may want to secure the API with an API key, integrate the API with an API gateway, check out how your [API is being consumed and used](https://www.moesif.com/features/api-analytics?utm_campaign=DevTo&utm_source=placed-article&utm_medium=body-cta&utm_content=building-aws-gateway-python), or build revenue through [API monetization](https://www.moesif.com/solutions/metered-api-billing?utm_campaign=DevTo&utm_source=placed-article&utm_medium=body-cta&utm_content=building-aws-gateway-python)? For a solution to your API analytics and monetization needs, [check out Moesif](https://www.moesif.com/wrap?onboard=true&utm_campaign=DevTo&utm_source=placed-article&utm_medium=body-cta&utm_content=building-aws-gateway-python) today to explore all of this and more!