refactor python hw with tabs (#2839)

* refactor python hw with tabs

* fix for tests failure

* fix for tests failure

* fix for tests failure

* address review comments

* review comments

* review comments

docs/serving/samples/hello-world/helloworld-python/index.md

@@ -5,4 +5,231 @@ weight: 1
 type: "docs"
 ---
 
-{{% readfile file="README.md" %}}
+This guide describes the steps required to create the `helloworld-python` sample
+app and deploy it to your cluster.
+
+The sample app reads a `TARGET` environment variable, and prints
+`Hello ${TARGET}!`. If `TARGET` is not specified, `World` is used as the default
+value.
+
+You can also download a working copy of the sample, by running the following
+commands:
+
+```shell
+git clone -b "{{< branch >}}" https://github.com/knative/docs knative-docs
+cd knative-docs/docs/serving/samples/hello-world/helloworld-python
+```
+
+## Prerequisites
+
+- A Kubernetes cluster with Knative installed and DNS configured. Follow the
+  [installation instructions](../../../../install/README.md).
+- [Docker](https://www.docker.com) installed and running on your local machine,
+  and a Docker Hub account configured.
+- (optional) The Knative CLI client
+  [kn](https://github.com/knative/client/releases) can be used to simplify the
+  deployment. Alternatively, you can use `kubectl`, and apply resource files
+  directly.
+
+## Build
+
+1. Create a new directory and cd into it:
+
+   ```shell
+   mkdir app
+   cd app
+   ```
+
+1. Create a file named `app.py` and copy the code block below into it:
+
+   ```python
+   import os
+
+   from flask import Flask
+
+   app = Flask(__name__)
+
+   @app.route('/')
+   def hello_world():
+      target = os.environ.get('TARGET', 'World')
+      return 'Hello {}!\n'.format(target)
+
+   if __name__ == "__main__":
+      app.run(debug=True,host='0.0.0.0',port=int(os.environ.get('PORT', 8080)))
+
+   ```
+
+1. In your project directory, create a file named `Dockerfile` and copy the code
+   block below into it. See
+   [official Python docker image](https://hub.docker.com/_/python/) for more
+   details.
+
+   ```docker
+   # Use the official lightweight Python image.
+   # https://hub.docker.com/_/python
+   FROM python:3.7-slim
+
+   # Allow statements and log messages to immediately appear in the Knative logs
+   ENV PYTHONUNBUFFERED True
+
+   # Copy local code to the container image.
+   ENV APP_HOME /app
+   WORKDIR $APP_HOME
+   COPY . ./
+
+   # Install production dependencies.
+   RUN pip install Flask gunicorn
+
+   # Run the web service on container startup. Here we use the gunicorn
+   # webserver, with one worker process and 8 threads.
+   # For environments with multiple CPU cores, increase the number of workers
+   # to be equal to the cores available.
+   CMD exec gunicorn --bind :$PORT --workers 1 --threads 8 --timeout 0 app:app
+   ```
+
+1. Create a `.dockerignore` file to ensure that any files related to a local
+   build do not affect the container that you build for deployment.
+
+   ```ignore
+   Dockerfile
+   README.md
+   *.pyc
+   *.pyo
+   *.pyd
+   __pycache__
+   ```
+
+  **NOTE:** Use Docker to build the sample code into a container. To build and
+  push to Docker Hub or container registry of your choice, run these commands replacing `{username}` with your Docker Hub username or the URL of the container registry.
+
+1. Use Docker to build the sample code into a container, then push the container
+   to the Docker registry:
+
+   ```shell
+   # Build the container on your local machine
+   docker build -t {username}/helloworld-python .
+
+   # Push the container to docker registry
+   docker push {username}/helloworld-python
+   ```
+
+## Deploying the app
+
+1. After the build has completed and the container is pushed to Docker Hub, you
+   can deploy the app into your cluster.
+
+   {{< tabs name="helloworld_python" default="kn" >}} {{% tab name="yaml" %}}
+
+   1. Create a new file, `service.yaml` and copy the following service
+      definition into the file. Make sure to replace `{username}` with your
+      Docker Hub username or with the URL provided by your container registry
+
+      ```yaml
+      apiVersion: serving.knative.dev/v1
+      kind: Service
+      metadata:
+        name: helloworld-python
+        namespace: default
+      spec:
+        template:
+          spec:
+            containers:
+              - image: docker.io/{username}/helloworld-python
+                env:
+                  - name: TARGET
+                    value: "Python Sample v1"
+      ```
+
+   Ensure that the container image value in `service.yaml` matches the container
+   you built in the previous step. Apply the configuration using `kubectl`:
+
+   ```shell
+   kubectl apply --filename service.yaml
+   ```
+
+   {{< /tab >}} {{% tab name="kn" %}}
+
+   With `kn` you can deploy the service with
+
+   ```shell
+   kn service create helloworld-python --image=docker.io/{username}/helloworld-python --env TARGET="Python Sample v1"
+   ```
+
+   This will wait until your service is deployed and ready, and ultimately it
+   will print the URL through which you can access the service.
+
+   {{< /tab >}} {{< /tabs >}}
+
+   During the creation of your service, Knative performs the following steps:
+
+   - Creates a new immutable revision for this version of the app.
+   - Network programming to create a route, ingress, service, and load balance
+     for your app.
+   - Automatically scales your pods up and down, including scaling down to zero
+     active pods.
+
+## Verification
+
+1. Run one of the followings commands to find the domain URL for your service.
+   > Note: If your URL includes `example.com` then consult the setup instructions for
+   > configuring DNS (e.g. with `xip.io`), or [using a Custom Domain](../serving/using-a-custom-domain.md).
+
+   {{< tabs name="service_url" default="kn" >}} {{% tab name="kubectl" %}}
+
+   ```shell
+   kubectl get ksvc helloworld-python  --output=custom-columns=NAME:.metadata.name,URL:.status.url
+   ```
+
+   Example:
+
+   ```shell
+   NAME                      URL
+   helloworld-python    http://helloworld-python.default.1.2.3.4.xip.io
+   ```
+
+   {{< /tab >}} {{% tab name="kn" %}}
+
+   ```shell
+   kn service describe helloworld-python -o url
+   ```
+
+   Example:
+
+   ```shell
+   http://helloworld-python.default.1.2.3.4.xip.io
+   ```
+
+   {{< /tab >}} {{< /tabs >}}
+
+1. Now you can make a request to your app and see the result. Replace the URL
+   below with the URL returned in the previous command.
+
+   Example:
+
+   ```shell
+   curl http://helloworld-python.default.1.2.3.4.xip.io
+   Hello Python Sample v1!
+
+   # Even easier with kn:
+   curl $(kn service describe helloworld-python -o url)
+   ```
+
+   > Note: Add `-v` option to get more detail if the `curl` command failed.
+
+## Removing
+
+To remove the sample app from your cluster, delete the service record.
+
+{{< tabs name="delete" default="kn" >}} {{% tab name="kubectl" %}}
+
+```shell
+kubectl delete --filename service.yaml
+```
+
+{{< /tab >}} {{% tab name="kn" %}}
+
+```shell
+kn service delete helloworld-python
+```
+
+{{< /tab >}} {{< /tabs >}}