Software development best practices

Passing configuration to application:
./myapp --database-url=... --port=123 ---loglevel=info

Using configuration inside application:

# .myapp.py
def get_arguments_parser():

    parser = argparse.ArgumentParser()
    parser.add_argument("--database-url")
    parser.add_argument("--port")
    parser.add_argument("--loglevel")

    return parser


def foo(database_url):

    print("Doing something with {}".format(database_url))


def main():

    parser = get_arguments_parser()
    arguments = parser.parse_args()

    foo(arguments["database_url"])

Disadvantages:
• a lot of typing, thus not very convenient
• easy to make a mistake
• doesn't scale

Passing configuration to application:
DATABASE_URL=... PORT=123 LOGLEVEL=info ./myapp
Suffers from exactly same problems as above

OR

# .bashrc
export DATABASE_URL=...
export PORT="123"
export LOGLEVEL="info"

Then from command line:
source ~/.bashrc
./myapp

Using configuration inside application:

# .myapp.py
import os

def foo():

    database_url = os.environ["DATABASE_URL"]
    print("Doing something with {}".format(database_url))


def main():

    foo()

Disadvantages:
• Configuration isn't stored in project, thus can't be version controlled
• Environment variables are essentially globals, so it's hard to see all inputs to a given piece of code

Define configuration file:

# ./configurations/development_config.yaml
DATABASE_URL=...
PORT="123"
LOGLEVEL="info"

Passing configuration to application:
./myapp --config-path=./configuration/development_config.yaml

Using configuration inside application:

# .myapp.py
import yaml

def get_arguments_parser():

    parser = argparse.ArgumentParser()
    parser.add_argument("--config-path")

    return parser


def foo(database_url):

    print("Doing something with {}".format(database_url))


def main():

    parser = get_arguments_parser()
    arguments = parser.parse_args()

    with open(arguments["config-path"]) as file:

        config = yaml.loads(file)

    foo(config["database_url"])

Advantages:
• Version controlled
• Easy to add new options
• Visible in code