Step-by-Step Guide: Writing a Buildspec File for a Python Application in AWS CodeBuild

AWS CodeBuild is a fully managed continuous integration service that enables developers to automate the building, testing, and deployment of their applications. In this tutorial, we will walk you through the process of writing a buildspec.yml file for a Python application in AWS CodeBuild. The buildspec.yml file defines the build settings and actions for CodeBuild, allowing you to customize the build process according to your project's requirements.

Step 1: Understanding the Project Structure Before diving into writing the buildspec.yml file, it's important to understand the structure of your Python project. Make sure you have the following components in place:

• Python source code files

• Required dependencies and packages specified in a requirements.txt file or similar

• Any additional configuration files or assets

Step 2: Creating the buildspec.yml File In the root directory of your project, create a new file named "buildspec.yml." This file will contain the build specifications for CodeBuild.

Step 3: Defining the Build Phases In the buildspec.yml file, start by defining the build phases required for your Python application. Typical phases include install, pre_build, build, post_build, and finalize. Here's an example buildspec.yml file with the install phase:

version: 0.2

phases:
  install:
    runtime-versions:
      python: 3.9
    commands:
      - pip install -r requirements.txt

In this example, the install phase installs the required dependencies specified in the requirements.txt file using pip.

Step 4: Configuring Additional Phases You can add more phases to the buildspec.yml file to perform specific actions during the build process. For instance, the build phase can be used to build your Python application and the test phase can be used to run unit tests. Modify your buildspec.yml file as follows:

version: 0.2
phases:
  install:
    runtime-versions:
      python: 3.9
    commands:
      - pip install -r requirements.txt
  build:
    commands:
      - python setup.py build
  test:
    commands:
      - python -m unittest discover

In this example, the build phase runs the setup.py build command to build your Python application and the test phase executes the unit tests using python -m unittest discover.

Step 5: Including Additional Phases and Commands You can continue adding phases and commands to the buildspec.yml file as per your project requirements. For instance, you may have a package phase to create a distribution package for your application:

version: 0.2
phases:
  install:
    runtime-versions:
      python: 3.9
    commands:
      - pip install -r requirements.txt
  build:
    commands:
      - python setup.py build
  test:
    commands:
      - python -m unittest discover
  package:
    commands:
      - python setup.py sdist bdist_wheel

In this example, the package phase uses setup.py to create a distribution archive and a wheel file for your Python application.

Step 6: Specifying Artifacts Define the artifacts generated during the build process that you want to upload to a designated location. These artifacts can include the built application, test reports, or any other relevant files. Specify the desired location and format of the artifacts in the buildspec.yml file. For example:

version: 0.2

phases:
  install:
    runtime-versions:
      python: 3.9
    commands:
      - pip install -r requirements.txt
  build:
    commands:
      - python setup.py build
  test:
    commands:
      - python -m unittest discover
  package:
    commands:
      - python setup.py sdist bdist_wheel
artifacts:
  files:
    - dist/*  # Uploads all files under the 'dist' directory as artifacts

In this example, the artifacts section specifies that all files under the dist directory should be uploaded as artifacts.

Reference :

AWS.amazon.com-user guide-build-spec-ref