Example of how to use python with bazel

Prerequisites

Following tools are expected to be preinstalled on your machine:

1. brew install poetry poetry is a python packaging and dependency management tool.

2. brew install bazelisk bazel is a tool for automating building and testing of software. Bazelisk ensures that you always use the version of Bazel specified in .bazelversion.

Setup with bazel

WORKSPACE needs to be in the root directory and imports necessary packages for bazel, such as installing dependenies with poetry. Notice a custom script for installing dependcies with poetry in build/rules/poetry.bzl.

Alle sub directories has a BUILD.bazel file. This can be empty.

Simple_greet: Simple python example

See the very simple python example in src/simple_greet

# first cd into the directory
cd src/simple_greet

# run the code through bazel with
bazel run :hello
# this allow you to run the code without having to create a container

# build binary for simple_greet with bazel
bazel build hello

# run the binary
cd ...
bazel-bin/src/simple_greet/hello
# expect "Hello, Simon" returned

Greet_any_name: Python example with input arguments

# first cd into the directory
cd src/greet_any_name

# run the code through bazel with
bazel run :hello-name
# expected return is "Hello, Simon-Stavland"

# changing the input argument in BUILD.bazel would allow the return o another name

flask_service: Simple flask service

See the simple flask service example in src/flask_service

Notice here that there are added dependencies for both the py_library and the py_binary. The exact version of these dependencies is handled through poetry.

# first cd into the directory
cd src/flask_service

# run the code with bazel
bazel run :run

you will see a lot of output in the terminal and the service is now up and running at http://0.0.00:5050. By going to http://0.0.00:5050/health/ you will se the return of the function health in app.py.