# rspivak/lsbasi

Let's Build A Simple Interpreter

Repository: https://github.com/rspivak/lsbasi
Canonical: https://ross.abutalabs.com/products/lsbasi
Language: Python
License: MIT
License Family: permissive
Last push: 2025-08-18T19:48:35+00:00

## Health v2 (maintenance only)
Score: 49/100 (v2, computed 2026-09-03T02:20:16.233290+00:00)
- activity 37, release rhythm 35, longevity 100
- inputs: {"age_days": 4097, "days_push": 380, "days_rel": null, "gap_med": null, "n_releases_24m": 0}
- flags: no_releases
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 1874, forks 422 (observed 2026-08-28T04:05:47.315244+00:00)

## What it is
Source code and examples for the 'Let's Build A Simple Interpreter' blog series, which teaches how to build a basic interpreter in Python step by step. It covers lexing, parsing, abstract syntax trees, semantic analysis, scopes, and procedure calls across 19 parts.

## Use cases
- learn how to build an interpreter from scratch
- understand lexers and parsers hands-on
- study abstract syntax trees with runnable code
- learn how call stacks and activation records work
- teach compiler fundamentals with a guided series

## When to choose
- you want a tutorial-style, incremental introduction to interpreters
- you prefer learning by running and extending working Python code
- you need a gentle on-ramp to compilers and language implementation

## When to avoid
- you need a production-ready interpreter or language runtime
- you want a comprehensive compiler textbook or formal theory course
- you need a modern language toolchain rather than educational code

## Facets
- artifact type: learning-resource
- maturity: stable
- function: interpreter, parser, compiler, programming-language
- domain: tutorials, compilers, programming-languages, parsers, education
- platform: python, cross-platform
- tags: interpreter-tutorial, blog-series, lexing, parsing, abstract-syntax-trees, pascal

## Member repositories
- rspivak/lsbasi (main) score 49

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:05:47.315244+00:00.
- Health v2: computed from the inputs above; adoption is never an input.
- Inferred fields (summary, facets, guidance): AI-extracted, prompt v1, taxonomy v1, on 2026-08-30T03:14:48.419797+00:00, confidence not recorded.
  - readme: https://github.com/rspivak/lsbasi (fetched 2026-08-28T04:05:47.315244+00:00, sha c4664cfaafff)
- Data as of 2026-08-30T08:39:29.467469+00:00.