yayaya

„Ja, ja, YAML schon wieder.“ — Every backend dev in Berlin, probably.

yayaya is a tiny helper for Yet Another YAml YArd (look, the letters lined up and we ran with it). It loads one YAML file—or several merged in order—lets you read nested keys with dot notation, and expands ${ENV_VAR} placeholders so secrets can live in the environment where they belong—not committed next to your instruction: prompts.

No framework. No magic beans. Just pyyaml and the sound of your PM saying jajaja when you tell them config is “basically done.”

Install

pip install yayaya

Or point pip at this repo if you live on the edge.

Quick start

from yayaya import init, get, contains

init("/path/to/config.yaml")

title = get("app.title", default="Untitled")
db_url = get("database.url", required=True)

if contains("features.experimental"):
    ...

Multiple files (layered config)

Pass a list: earlier files are the base, later ones override. Nested dicts are deep-merged; scalars and lists are replaced entirely by the newer file. Expansion runs once on the merged result.

init(["/etc/myapp/defaults.yaml", "/instance/config.yaml", "/instance/local.yaml"])

Useful for defaults + tenant config + secrets-by-path without copy-pasting huge trees.

${ENV_VAR} expansion

After parsing YAML, all strings are walked recursively. Placeholders like ${API_KEY} are replaced with values from os.environ. Missing variables become empty strings.

# config.yaml
service:
  api_key: "${API_KEY}"
  port: 8080

import os
from yayaya import init, get

os.environ["API_KEY"] = "secret"
init("config.yaml")
assert get("service.api_key") == "secret"
assert get("service.port") == 8080

You can also run expansion yourself (e.g. on a dict you built elsewhere):

from yayaya import expand_env_placeholders

data = expand_env_placeholders({"x": "${HOME}"}, environ=os.environ)

API

Function	Purpose
init(path)	Load one YAML file, or init([p1, p2, ...]) to merge left → right.
get(key, default=None, required=False)	Dot-path lookup ("db.pool.size").
contains(key)	Whether the path exists.
reload_config()	Re-read the same path(s) in the same order.
override_config_path(path)	Same as init (one path or a list).
config_paths()	Absolute paths last passed to init / override_config_path.
deep_merge(a, b)	Deep-merge two dict-like trees (lists replaced, not spliced).
expand_env_placeholders(value, environ=None)	Recursive ${VAR} substitution.

Exceptions (all subclass ConfigError): ConfigNotLoadedError, ConfigFileNotFoundError, ConfigKeyNotFoundError.

Development

pip install -e ".[dev]"
python -m unittest discover -s tests -v

License

Whatever the repo owner says—ask Karel if you’re unsure.

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If YAML were a conversation, yayaya is the part where you nod three times and actually read the file.