python

sourceacademy-sicp

The Source Academy Python standard library, packaged for plain CPython.

Source Academy runs a subset of Python (via py-slang) that adds a standard library for the Structure and Interpretation of Computer Programs (SICP) — pair, head, tail, llist, the math_* functions, streams, and so on. This package provides those same names to ordinary CPython, so that code written for CS1101S or the SICP Python edition runs the same way on your own machine.

Install

pip install sourceacademy-sicp

Use

Put this at the top of your program:

from sicp import *

Then the Source Academy Python standard library is available:

xs = llist(1, 2, 3)
print(xs)                       # [1, [2, [3, None]]]
print_llist(xs)                 # llist(1, 2, 3)
print(list_length([1, 4, 9, 16, 25]))                # 5
print(math_sqrt(2))             # 1.4142135623730951
print(eval_stream(integers_from(1), 4))              # [1, [2, [3, [4, None]]]]

Representation

A pair is a two-element Python list [head, tail], and the empty list is None — exactly as in Source Academy Python. A two-element list is therefore also a pair (is_pair and is_list are both true), matching the frontend's value model, so results print and compare directly against the textbook:

pair("x", 9)      # ['x', 9]
llist(1, 2, 3)    # [1, [2, [3, None]]]

What's included

The library mirrors the groups in py-slang's standard library:

submodule	provides
sicp.misc	error, arity, real, imag, is_none / is_integer / is_float / is_complex / is_string / is_boolean / is_function / is_number, random_random, time_time
sicp.math	math_pi, math_e, math_tau, math_inf, math_nan, and the math_* functions (math_sqrt, math_sin, math_floor, math_comb, …)
sicp.linked_list	pair, head, tail, is_pair, llist, print_llist, plus map, filter, reduce, reverse, append, length, member, remove, enum_llist, …
sicp.pair_mutators	set_head, set_tail
sicp.list	is_list, list_length, equal
sicp.stream	stream, stream_map, stream_filter, stream_ref, integers_from, eval_stream, …

from sicp import * brings the whole superset into scope, mirroring the environment students have in Source Academy's Python.

For the full documentation of every function — signatures, descriptions, and worked examples — see the Python §4 standard library reference. Its groups (MISC, MATH, LINKED LISTS, PAIR MUTATORS, LISTS, STREAM, MCE) correspond to the sicp.<group> submodules above.

Compatibility

• Requires Python 3.10+.
• is_number mirrors Scheme's number? primitive as used in the textbook.
• round, abs, len, max, min, str, repr, int, float, complex, bool, print, and input are plain CPython builtins, not reimplementations of Source Academy Python's versions, so a few edge cases differ:
  • arity() raises on a handful of CPython builtins whose signature isn't introspectable (e.g. arity(print), arity(max), arity(min), arity(str)), where Source Academy Python's own arity returns a value.
  • is_function(int) and is_function(str) are True here, since CPython's callable() treats classes as callable — Source Academy Python's tag-based check would say False.
  • max/min accept the single-iterable form (max([1, 2, 3])); Source Academy Python's versions require two or more direct arguments.

Source & development

This package lives in the py-slang repository under python/. py-slang is the reference implementation of Source Academy Python, so keeping the library here — next to the standard library it mirrors (src/stdlib/) — is what keeps the two from drifting apart. Each sicp.<group> submodule corresponds to a py-slang stdlib group.

cd python
python -m pip install -e .        # editable install for development
python -m pytest                  # or: PYTHONPATH=. python tests/test_sicp.py
python -m build                   # build the wheel + sdist

Releasing

Publishing to PyPI is not automatic on push or merge. The CI test job runs on every change under python/**, but the publish job runs only when a GitHub Release is published (.github/workflows/python-package.yml).

One-time setup: configure a PyPI Trusted Publisher for the sourceacademy-sicp project pointing at this repository and the python-package workflow (or swap the publish step for a token-based upload).

To cut a release:

1. Bump version in pyproject.toml. PyPI rejects re-uploads of an existing version, so this must change every time.
2. Merge to main.
3. Create and publish a GitHub Release (a tag such as sicp-vX.Y.Z). Publishing it triggers the publish job, which builds the wheel + sdist and uploads them to PyPI.

License

Apache-2.0. Part of the Source Academy project.