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Kompoz

Composable Predicate & Transform Combinators for Python

Python 3.13+ License: MIT

Kompoz lets you build complex validation rules and data pipelines using intuitive Python operators. Instead of nested if/else statements, write declarative, composable logic:

from dataclasses import dataclass
from kompoz import rule, rule_args


@dataclass
class User:
    name: str
    is_admin: bool = False
    is_active: bool = True
    is_banned: bool = False
    account_age_days: int = 0
    credit_score: int = 500


@rule
def is_admin(user):
    return user.is_admin

@rule
def is_active(user):
    return user.is_active

@rule_args
def account_older_than(user, days):
    return user.account_age_days > days

# Combine with operators - reads like English!
can_access = is_admin | (is_active & account_older_than(30))

# Use it
ok, _ = can_access.run(user)

Features

  • Operator Overloading --- Use & (and), | (or), ~ (not), >> (then) for intuitive composition
  • Conditional Branching --- if_then_else() and ternary ?: for explicit control flow
  • Decorator Syntax --- Clean @rule and @rule_args decorators
  • Parameterized Rules --- account_older_than(30) creates reusable predicates
  • Validation with Errors --- @vrule / @async_vrule decorators collect all error messages
  • Expression DSL --- Human-readable rule expressions with AND/OR/NOT/IF/THEN/ELSE
  • Async Support --- Full async/await support with tracing, validation, and parallel execution
  • Caching --- @cached_rule and use_cache() to memoize expensive predicates
  • Time-Based Rules --- during_hours(), on_weekdays(), after_date(), and more
  • Error Tracking --- Transforms track exceptions via last_error attribute
  • Retry with Observability --- Built-in retry logic with hooks for monitoring
  • Zero Dependencies --- Core library has no external dependencies

Quick Install

pip install kompoz

uv add kompoz

Next Steps