Introduction
There are times when we are in a dilemma as to how to properly use application environments. It gets confusing really fast. I will try to explain the approach (that I see) makes sense.
I will be using Python in this blog, but this implementation is agnostic of the programming language.
Pre-requisites
- Python 3.8.x or higher
- PyYaml library - To read our YAML configuration files
Lets get started!
- Create a
yamlfile just like below
# settings.yml
default: &default
api_url: "https://example.com/dev"
aws: &aws
s3_bucket:
- my-bucket
dev: &dev
<<: *default
test: &test
<<: *default
api_url: "https://example.com/test"
prod: &prod
<<: *default
api_url: "https://prod.example.com/"
aws:
<<: *aws
s3_bucket:
- my-prod-bucket
In the above yaml, we are using the inheritance to override the configurations for individual environments.
- To pass the correct configuration, we can leverage
argparsewhich parses command-line arguments for us. The following python script does that.
# main.py
import argparse
def read_cli_arguments():
arg_parser = argparse.ArgumentParser()
arg_parser.add_argument(
"--app-env",
required=True,
action="store",
choices=("prod", "dev", "test"),
help="Application environment to run in"
)
return arg_parser.parse_args()
- Next, we read the configuration file based on the environment
# main.py
from typing import Dict
import yaml
def read_settings(app_env: str) -> Dict:
try:
with open("settings.yml", mode="r", encoding="utf-8") as config:
configs: Dict = yaml.safe_load(config)
except yaml.YAMLError as yaml_err:
print(f"Error occurred while reading the file. Error: {yaml_err}")
raise
return configs[app_env]
- Reading the configuration dictionary is now as easy as
# main.py
settings_prod: Dict = read_settings("prod")
print(f"Prod Configurations: {settings_prod}")
settings_test: Dict = read_settings("test")
print(f"Test Configurations: {settings_test}")
- Finally, we use this as part of running our
main.pyfile from the command-line like this
$ ls
main.py settings.yml
$ python3 main.py --app-env prod
Complete Code
# main.py
from typing import Dict
import argparse
import yaml
def read_cli_arguments():
arg_parser = argparse.ArgumentParser()
arg_parser.add_argument(
"--app-env",
required=True,
action="store",
choices=("prod", "dev", "test"),
help="Application environment to run in"
)
return arg_parser.parse_args()
def read_settings(app_env: str) -> Dict:
try:
with open("settings.yml", mode="r", encoding="utf-8") as config:
configs: Dict = yaml.safe_load(config)
except yaml.YAMLError as yaml_err:
print(f"Error occurred while reading the file. Error: {yaml_err}")
raise
return configs[app_env]
# Program Execution Starts Here
if __name__ == "__main__":
# Read CLI arguments
args = read_cli_arguments()
# Retrieve specific configurations
settings: Dict = read_settings(app_env=args.app_env)
print(f"Configs: {settings}")
Executing the above code on the terminal
$ python3 main.py --app-env prod
Configs: {"api_url": "https://prod.example.com/", "aws": {"s3_bucket": ["my-prod-bucket"]}}
Top comments (1)
Thanks mate!