cons
An implementation of Lisp/Scheme-like cons in Python.
Decision gist · record as of 2026-08-14
Yes, if you need Lisp/Scheme-style cons operations for functional programming or symbolic computation. Install friction is minimal and maintenance is active. However, verify the license terms first—the license status is unclear and must be confirmed before use in proprietary or copyleft-sensitive contexts.AI-flagged interpretation of the facts on this page — verify before relying
Before you install
- Requires Python 3.9 or later.
- Low install friction with a single pure-Python dependency (logical-unification).
- Actively maintained with recent commits and a stable release cycle; marked Alpha but supports current Python versions (3.9+).
License · maintenance · safety
(unclear) — License status is unclear—no SPDX identifier or raw license text is available. Verify the actual license terms before using in proprietary or copyleft-sensitive projects.
last release 2025-07-11 (399 days) · last repo commit 2026-04-28 · 12 stars
0 known vulnerabilities (OSV.dev, 2026-08-14) · 1,277,357 downloads/mo, #4,123 on PyPI
Alternatives
Verify before relying
pip install cons
from cons import cons, car, cdr
result = cons(1, [2, 3])
print(result) # [1, 2, 3]
print(car(result)) # 1
print(cdr(result)) # [2, 3]- Whether the unclear license permits use in closed-source or commercial projects.
- Performance characteristics when working with very large sequences or deeply nested cons operations.
What it is and what it does
The cons package brings Lisp and Scheme's classic cons-cell operations into Python, letting you build and decompose sequences using car (head), cdr (tail), and cons (prepend) functions. It works across Python's standard sequence types—lists, tuples, iterators, and OrderedDicts—while treating None as the empty list, following Scheme conventions. The package also integrates with the logical-unification library, enabling pattern matching and unification on cons structures.
It's designed for developers working with functional programming patterns or symbolic computation in Python. The implementation respects Python's sequence semantics while staying true to Lisp/Scheme behavior; for example, calling car or cdr on an empty sequence raises ConsError rather than returning nil. You can customize which types participate in cons operations by registering them with the MaybeCons and NonCons abstract base classes.
Use it for
- Build functional data structures using cons pairs in symbolic or logic programming applications.
- Perform pattern matching and unification on Python sequences using the unification integration.
- Implement recursive list algorithms that rely on car/cdr decomposition in a Lisp-like style.
- Work with OrderedDicts and other sequence types using uniform cons semantics.
- Prototype or port Scheme/Lisp algorithms to Python while preserving their list-manipulation idioms.
Worth the install?
AI-flagged interpretation of the facts on this page. Verify before relying on it.
Yes, if you need Lisp/Scheme-style cons operations for functional programming or symbolic computation.
Install friction is minimal and maintenance is active. However, verify the license terms first—the license status is unclear and must be confirmed before use in proprietary or copyleft-sensitive contexts.
Install
cons on PyPI
Before you install
Low install friction with a single pure-Python dependency (logical-unification). Actively maintained with recent commits and a stable release cycle; marked Alpha but supports current Python versions (3.9+).
Requires Python 3.9 or later.
License in practice
License status is unclear—no SPDX identifier or raw license text is available. Verify the actual license terms before using in proprietary or copyleft-sensitive projects.
Quickstart
pip install cons
from cons import cons, car, cdr
result = cons(1, [2, 3])
print(result) # [1, 2, 3]
print(car(result)) # 1
print(cdr(result)) # [2, 3]Verify before relying
- Whether the unclear license permits use in closed-source or commercial projects.
- Performance characteristics when working with very large sequences or deeply nested cons operations.
Package facts
| License | Not declared unclear |
| Python support | Supports the current Python release >=3.9 |
| Install friction | Low. Pure-Python wheel |
| Runtime dependencies | 1 packagelogical-unification |
| Maintenance | Actively maintained 399 days since the last release |
| Last repo commit | |
| First released | |
| Downloads | 1,277,357 / month, #4,123 on PyPI 30-day window, as of 2026-08-14 |
| Known vulnerabilities | None known OSV.dev, checked 2026-08-14 |
| Classifiers | Development Status :: 3 - AlphaIntended Audience :: DevelopersIntended Audience :: Science/ResearchOperating System :: OS IndependentProgramming Language :: PythonProgramming Language :: Python :: 3Programming Language :: Python :: 3.10Programming Language :: Python :: 3.11Programming Language :: Python :: 3.9Programming Language :: Python :: Implementation :: CPythonProgramming Language :: Python :: Implementation :: PyPyTopic :: Software Development :: Libraries |
Evidence: cons-0.4.7-py3-none-any.whl
Tags
Let your AI agent find packages like this
Example. Real query, live index.
You found this page by searching. An agent finds it by wishing: SkillFed indexes 14,416 PyPI packages by what they can do, searchable in plain language.
wish › “lisp cons car cdr python”
- consImplements Lisp/Scheme-style cons operations (cons, car, cdr) for…
- sexpdataParses and serializes S-expressions (Lisp-style symbolic expressions)…
- abnumberAbNumber provides Python APIs to number and align antibody sequences…
Give your agent the search over MCP, or paste the wish link into any chat.
More Libraries packages
urllib3 is an HTTP client library that provides thread-safe connection pooling, SSL/TLS verification, multipart file uploads, request retries, compression support, and proxy handling for Python applications.
Requests is a Python HTTP library that simplifies sending HTTP/1.1 requests with automatic handling of headers, authentication, cookies, and response parsing.
Pluggy provides a plugin system that lets you define hook specifications and register implementations to be called in sequence, enabling extensible Python applications without tight coupling.
Install it if you're building an extensible application or framework.
Provides parsing, arithmetic, and recurrence rule computation for dates and times, with timezone support and iCalendar RFC compliance.
Install it if you need to parse flexible date strings, compute relative dates, handle timezones, or work with recurrence rules—it's the de facto choice for these tasks.
Six provides utility functions to write Python code that runs on both Python 2.7 and Python 3.3+, smoothing over language differences between the two versions.
pytest is a testing framework that lets you write test functions using plain assert statements and automatically discovers and runs them, with detailed failure reporting.
See also snuggs · logical-unification · funcy · pampy · pipe · ordereddict · infinity · funcparserlib · Expression · etuples