cfx 0.4.0

Lightweight self-documenting configuration classes via Python descriptors.

cfx

Declare configuration fields next to the classes that use them. Each field carries its own default, type checking, and documentation. Compose any set of configs into a larger one, flat or nested, and get serialization, CLI integration, and a self-documenting display for free.

from cfx import Config, Float, String, Bool

class CalibConfig(Config):
    """Photometric calibration parameters."""
    confid = "calib"
    scale = Float(1.0, "Flux scale factor")
    zero_point = Float(25.0, "Photometric zero-point")

class SourceConfig(Config, components=[CalibConfig]):
    """Source detection and measurement."""
    confid = "source"
    n_sigma = Float(3.0, "Detection threshold in sigma")

class PipelineConfig(Config, components=[SourceConfig]):
    """Image analysis pipeline."""
    confid = "pipeline"
    run_id = String("run_01", "Run identifier")
    dry_run = Bool(False, "Validate only; skip writes")

cfg = PipelineConfig()
print(cfg)

PipelineConfig: Image analysis pipeline.
└─ SourceConfig: Source detection and measurement.
    └─ CalibConfig: Photometric calibration parameters.
Config         | Key        | Value  | Description
---------------+------------+--------+-----------------------------
PipelineConfig | run_id     | run_01 | Run identifier
PipelineConfig | dry_run    | False  | Validate only; skip writes
SourceConfig   | n_sigma    | 3.0    | Detection threshold in sigma
CalibConfig    | scale      | 1.0    | Flux scale factor
CalibConfig    | zero_point | 25.0   | Photometric zero-point

• Validated fields — typos and bad values raise immediately at the point of assignment, not silently hours later.
• Self-documenting — print(cfg) renders a tree of the config hierarchy followed by a unified table of all fields, nested included. In Jupyter the same layout renders as HTML automatically via _repr_html_.
• Composable — assemble configs from multiple subsystem configs, flat or nested, or mix both styles. The same fields can be organized deeply for precision in code and re-exposed shallowly for users — bridging the gap between code structure and user-facing logic.
• Serializable — round-trip to/from dict, YAML, and TOML with one method call.
• CLI-ready — every config exposes add_arguments / from_argparse for argparse and click_options / from_click for Click. Nested sub-configs use dot-notation flags (e.g. --source.n-sigma).
• Extensible — subclass ConfigField to add your own field types with custom validation and normalization.
• Zero hard dependencies — YAML, TOML, and Click support are optional.

Installation

pip install cfx

With optional serialization and CLI backends:

pip install "cfx[yaml]"   # adds PyYAML
pip install "cfx[toml]"   # adds tomli-w
pip install "cfx[click]"  # adds Click
pip install "cfx[all]"    # everything

Quick start

from cfx import Config, Int, Float, String, Options, Bool, Path

class ProcessingConfig(Config):
    confid = "processing"
    iterations = Int(100, "Number of iterations", minval=1)
    threshold = Float(0.5, "Acceptance threshold", minval=0.0, maxval=1.0)
    label = String("run_01", "Human-readable run label")
    mode = Options(("fast", "balanced", "thorough"), "Processing mode")
    verbose = Bool(False, "Enable verbose logging")

cfg = ProcessingConfig()

# Dot access and dict-style access are interchangeable
cfg.iterations = 200
cfg["mode"] = "thorough"

# Bad values raise immediately
cfg.threshold = 1.5   # ValueError: Expected value <= 1.0, got 1.5

# Serialize to dict, YAML, or TOML
d = cfg.to_dict()
cfg2 = ProcessingConfig.from_dict(d)

# Copy with overrides, diff two instances
modified = cfg.copy(iterations=500)
cfg.diff(modified)   # {'iterations': (200, 500)}

Environment variables

Back any field with an environment variable — the value is read lazily, so the same class works across environments without subclassing:

class ServiceConfig(Config):
    host = String("localhost", "Database host", env="DB_HOST")
    port = Int(5432, "Port", env="DB_PORT")

# DB_HOST=prod.example.com python run.py
cfg = ServiceConfig()
cfg.host   # 'prod.example.com' — from env, no code change needed

CLI

Every config exposes add_arguments / from_argparse for argparse and click_options / from_click for Click. Nested sub-configs use dot-notation flags automatically:

import argparse

parser = argparse.ArgumentParser()
ProcessingConfig.add_arguments(parser)
cfg = ProcessingConfig.from_argparse(parser.parse_args())
# python run.py --iterations 200 --mode thorough --no-verbose

License

GPL-3.0-only — see LICENSE.