Python

Platform.sh supports deploying Python applications. Your application can use WSGI-based (Gunicorn / uWSGI) application server, Tornado, Twisted, or Python 3.5+ asyncio server.

Supported versions

WSGI-based configuration

In this example, we use Gunicorn to run our WSGI application. Configure the .platform.app.yaml file with a few key settings as listed below, a complete example is included at the end of this section.

Specify the language of your application (available versions are listed above):
```
# .platform.app.yaml
type: "python:3.6"
```
Build your application with the build hook. Assuming you have your pip dependencies stored in requirements.txt and a setup.py at the root of your application folder to execute build steps:
```
hooks:
  build: |
    pip install -r requirements.txt
    pip install -e .
    pip install gunicorn
```
These are installed as global dependencies in your environment.
Configure the command you use to start serving your application (this must be a foreground-running process) under the web section, e.g.:
```
web:
  commands:
    start: "gunicorn -b 0.0.0.0:$PORT project.wsgi:application"
```
This assumes the WSGI file is project/wsgi.py and the WSGI application object is named application in the WSGI file.
Define the web locations your application is using:
```
web:
  locations:
    "/":
      root: ""
      passthru: true
      allow: false
    "/static":
      root: "static/"
      allow: true
```
This configuration asks our web server to handle HTTP requests at "/static" to serve static files stored in /app/static/ folder while everything else is forwarded to your application server.
Create any Read/Write mounts. The root file system is read only. You must explicitly describe writable mounts.
```
mounts:
    tmp:
        source: local
        source_path: tmp
    logs:
        source: local
        source_path: logs
```
This setting allows your application writing files to /app/tmp and have logs stored in /app/logs.

Then, set up the routes to your application in .platform/routes.yaml.

   "https://{default}/":
     type: upstream
     upstream: "app:http"

Here is the complete .platform.app.yaml file:

name: app
type: python:2.7

web:
  commands:
    start: "gunicorn -b $PORT project.wsgi:application"
  locations:
    "/":
      root: ""
      passthru: true
      allow: false
    "/static":
      root: "static/"
      allow: true

hooks:
  build: |
    pip install -r requirements.txt
    pip install -e .
    pip install gunicorn

mounts:
   tmp:
       source: local
       source_path: tmp
   logs:
       source: local
       source_path: logs

disk: 512

Using the asyncio module

The above Gunicorn based WSGI example can be modified to use the Python 3.5+ asyncio module.

Change the type to python:3.6.

Change the start command to use asyncio.

web:
  commands:
    start: "gunicorn -b $PORT -k gaiohttp project.wsgi:application"

Add aiohttp as pip dependency in your build hook.

hooks:
  build: |
    pip install -r requirements.txt
    pip install -e .
    pip install gunicorn aiohttp

Connecting to services

You can define services in your environment. And, link to the services using .platform.app.yaml:

relationships:
    database: "mysqldb:mysql"

By using the following Python function calls, you can obtain the database details.

import base64
import json
import os

# Use str(base64.b64decode()) for py3k compatibility.
relationships = os.environ['PLATFORM_RELATIONSHIPS']
relationships = json.loads(str(base64.b64decode(relationships), 'utf-8'))

# Sample content of relationships['database']:
# [{
#   'scheme': 'mysql',
#   'host': 'database.internal',
#   'ip': '246.0.81.164'
#   'port': 3306,
#   'path': 'main',
#   'username': 'main',
#   'password': 'main',
#   'query': {'is_master': True},
# }]

Project templates

A number of project templates for Python applications are available on GitHub. Not all of them are proactively maintained but all can be used as a starting point or reference for building your own website or web application.