Therismos

θερισμός — Greek; noun — Harvest.

A Python library for modeling queries, filters, expressions, grouping, and aggregations as object structures.

Features

• Backend-agnostic modeling: Build expressions, filters, sorting, and aggregations independent of any specific backend
• Declarative DSL: Natural Python syntax for building complex queries
• Type safety: Optional field type declarations with automatic casting
• Immutable structures: All nodes are immutable and thread-safe
• Powerful optimizer: Detects contradictions, tautologies, and simplification opportunities
• Grammar-based serialization: Convert expressions to/from compact strings for URLs and APIs
• Visitor pattern: Extensible architecture for converting to any backend format
• Multiple backends: MongoDB, Polars, pandas, SQLAlchemy, SQLModel, and custom backends
• Expression templates: Parameterized, persistable filter expressions with a transform pipeline DSL
• Grouping and aggregation: Model grouping and aggregation criteria as objects
• Sorting specifications: Model sort criteria as objects with optimization and visitor support
• Field pruning: Remove or project field-based constraints with polarity-aware semantics

Installation

pip install therismos

Optional extras:

pip install therismos[mongodb]        # PyMongo / Motor
pip install therismos[polars]         # Polars DataFrames
pip install therismos[pandas]         # pandas DataFrames
pip install therismos[sqlalchemy]     # SQLAlchemy / SQLModel

Documentation

Full documentation is available at https://therismos.readthedocs.io.

License

MIT