This is the code example for blog - An implementation of Config class

config.py

import os
import yaml
from mergedeep import merge
from functools import reduce


class Config:

    class ValueDesc:
        def __init__(self, env_var, type=str, required=True, default=None):
            self.env_var = env_var
            self.type = type
            self.required = required
            self.default = default

    PARAMETERS = {
        "web.request.timeout": ValueDesc("WEB_MAX_REQUEST_TIMEOUT", type=int, required=False, default=600),
        "web.request.maxSize": ValueDesc("WEB_MAX_HEADER_SIZE", type=int, required=False, default=32768),
        "web.headers.clientType": ValueDesc("WEB_HEADERS_CLIENT_TYPE", type=str, required=True, default="Customize-Client"),
        "web.headers.maxSize": ValueDesc("WEB_HEADERS_MAX_SIZE", type=int, required=True, default=1024),
        "database.username": ValueDesc("DB_USERNAME", type=str, required=True),
        "database.password": ValueDesc("DB_PASSWORD", type=str, required=True),
        "database.schema": ValueDesc("DB_SCHEMA", type=str, required=True),
        "database.poolSize": ValueDesc("DB_POOL_SIZE", type=int, required=False, default=10)
    }

    def __init__(self):
        self.web_request_timeout = self._get_config_value("web.request.timeout")
        self.web_request_maxSize = self._get_config_value("web.request.maxSize")
        self.web_headers_clientType = self._get_config_value("web.headers.clientType")
        self.web_headers_maxSize = self._get_config_value("web.headers.maxSize")
        self.database_username = self._get_config_value("database.username")
        self.database_password = self._get_config_value("database.password")
        self.database_schema = self._get_config_value("database.schema")
        self.database_poolSize = self._get_config_value("database.poolSize")

    def generate_yaml_with_default_values(self):
        res = []

        for key, value in Config.PARAMETERS.items():
            items = key.split(".")[::-1]
            default = value.default
            x = reduce(lambda v, k: {k: default} if v is None else {k: v}, items, None)
            res.append(x)

        x = reduce(merge, res)
        return yaml.dump(x, default_flow_style=False)

    def _get_config_value(self, key):
        config_value = yaml.safe_load(open("config.yaml", "r").read())
        value = reduce(lambda data, k: data[k] if data and k in data else None, key.split('.'), config_value)
        value_desc = Config.PARAMETERS.get(key)

        if value is None:
            if not value_desc:
                return None
            value = os.getenv(value_desc.env_var, value_desc.default)
        return value


# config = Config()
# print(config.generate_yaml_with_default_values())
# print(config.web_request_timeout)
# print(config.web_request_maxSize)
# print(config.web_headers_clientType)
# print(config.web_headers_maxSize)
# print(config.database_username)
# print(config.database_password)
# print(config.database_schema)
# print(config.database_poolSize)

config.yaml

web:
  request:
    timeout: 1
    maxSize: 2
  headers:
    clientType: 'custom'
    maxSize: 3

database:
  username: "admin"
  password: "password"
  schema: "default"
  poolSize: 4