pycodemath 0.2.0

Token-efficient exact math for AI agents.

Write math in a few characters, get an exact answer or standalone, optimized Python/NumPy code back — instead of asking a language model to "do arithmetic in its head" or to hand-write numerical loops.

Built as a thin, disciplined layer over SymPy + NumPy:

1. Cut tokens — one short command in, one exact result out. Perfect as an agent tool (MCP server included).
2. Better code than naive Python — the generator applies symbolic simplification + common-subexpression elimination (CSE) before emitting code (measured ~1.7x faster than naive expansion on repeated subexpressions).

text → [parser] → IR (expression tree) → [engine]     evaluate / simplify / solve
                                       → [generator]  IR → CSE → Python/NumPy source

Install

pip install -e .                  # core: sympy + numpy
pip install -e .[mcp]             # + MCP server for AI agents
pip install -e .[dev]             # + pytest

Requires Python ≥ 3.11.

Quick start

One-shot CLI (scriptable)

Every command below is a real invocation with its real output.

$ python -m pycodemath "diff sin(x)*x dx"
x*cos(x) + sin(x)

$ python -m pycodemath "integrate 2*x dx"
x**2

$ python -m pycodemath "solve x^2 - 4 for x"
-2, 2

$ python -m pycodemath "sin(x)^2 + cos(x)^2"
1

$ python -m pycodemath "eig [[2,1],[1,2]]"
3, 1

$ python -m pycodemath "solve_nd x^2+y^2-4; x-y for x,y at 1,1"
x = 1.4142135623746899, y = 1.4142135623746899

Errors go to stderr with exit code 1, results to stdout with exit code 0 — safe to call from scripts and agent tools. On Windows consoles set PYTHONUTF8=1.

REPL

python -m pycodemath        # or just: pycodemath

Type help for the full command table (derivatives, integrals, equation solving, matrices, root finding, optimization, the whole ODE suite, and code generation).

MCP server (math for any AI agent)

pip install -e .[mcp]
claude mcp add pycodemath -- python -m pycodemath.cli.mcp_server

Exposes one tool, math_eval, that accepts the same commands as the REPL — an agent sends diff sin(x)*x dx and receives x*cos(x) + sin(x) exactly, with zero mental arithmetic.

Use it as a Claude Code skill

The MCP server above is the portable path — it plugs into any MCP client. If you specifically use Claude Code, you can also wire Pycodemath in as a skill, so Claude reaches for the engine on its own whenever a prompt needs real math (no MCP process to keep running).

What it changes: instead of computing "in its head" — where a large model can quietly get arithmetic, an integral, or an eigenvalue wrong — Claude shells out to the engine and pastes back an exact SymPy/NumPy result. One short command in, one exact line out: fewer tokens, no silent mistakes.

Deploy (once):

pip install pycodemath          # or: pip install -e .   (from a clone)
mkdir -p ~/.claude/skills/pycodemath

Save the following as ~/.claude/skills/pycodemath/SKILL.md:

---
name: pycodemath
description: Compute math with the local Pycodemath engine (SymPy+NumPy) instead
  of in your head — derivatives, integrals, solving equations and systems
  (linear and nonlinear), determinants/inverses/eigenvalues, gradients/Jacobians/
  Hessians, function minima, ODEs, and optimized Python/NumPy code generation
  (CSE). Use whenever the user asks to compute or verify symbolic/numerical math,
  or to generate code from a formula.
---

# Pycodemath — local math engine

One command = one call (the package is pip-installed, so any working directory):

    python -m pycodemath "<command>"

Result goes to stdout (exit 0); errors to stderr (exit 1). Power notation: `^` or `**`.
On Windows consoles, set `PYTHONUTF8=1`.

## Commands

| Command | Example |
|---|---|
| `<expression>` — simplify | `python -m pycodemath "sin(x)^2 + cos(x)^2"` → `1` |
| `diff <expr> d<var>` — derivative | `"diff sin(x)*x dx"` → `x*cos(x) + sin(x)` |
| `integrate <expr> d<var>` — symbolic integral | `"integrate 2*x dx"` → `x**2` |
| `solve <expr> for <var>` — solve = 0 | `"solve x^2-4 for x"` → `-2, 2` |
| `code <expr>` — CSE-optimized NumPy code | `"code (sin(x)+cos(x))^2"` |
| `det / inv / transpose / eig <A>` | `"eig [[2,1],[1,2]]"` → `3, 1` |
| `solve_system <A> = <b>` — linear system | `"solve_system [[2,1],[1,3]] = [3,5]"` |
| `root <expr> for <var> at <x0>` — numeric root | `"root x^2-2 for x at 1"` |
| `min <expr> for <var> at <x0> [method newton|bfgs]` — 1D minimum | `"min (x-3)^2 for x at 0"` |
| `grad <expr> for <x,y,...>` — symbolic gradient | `"grad x^2*y for x,y"` |
| `solve_nd <f1>; <f2> for <x,y> at <x0,y0>` — nonlinear system | `"solve_nd x^2+y^2-4; x-y for x,y at 1,1"` |
| `min_nd <expr> for <x,y> at <x0,y0> [method newton|bfgs]` — N-D minimum | `"min_nd (1-x)^2+100*(y-x^2)^2 for x,y at -1.2,1 method bfgs"` |
| limits / series / sums / ODEs | `"limit sin(x)/x for x to 0"`, `"sum 1/k^2 for k from 1 to oo"` |

Type `help` in the REPL (`python -m pycodemath`) for the full command table.

## Rules

- **When to use:** the user wants a concrete math result (derivative, integral,
  equation, matrix, minimum, ODE) or optimized code from a formula. The engine is
  exact — trust its output over mental arithmetic.
- **When not to use:** trivial arithmetic or conceptual questions with no compute.
- A `error: ...` line on stderr (exit 1) usually means a typo in the command, a
  numerical method that did not converge, or no real solution — read the message,
  it is specific.

Restart Claude Code (or open a new session) and it will invoke the skill automatically when a task needs exact math. To confirm it registered, run /help and look for pycodemath in the skills list.

Limits, series and symbolic sums

Beyond diff/integrate/solve, the engine handles limits (including one-sided and at infinity), Taylor/Laurent expansions and symbolic summation — finite or infinite. All real invocations with real outputs:

$ python -m pycodemath "limit (1+1/n)^n for n to oo"
E

$ python -m pycodemath "series exp(x) for x n 4"
x**3/6 + x**2/2 + x + 1

$ python -m pycodemath "sum k for k from 1 to n"
n**2/2 + n/2

$ python -m pycodemath "sum 1/k^2 for k from 1 to oo"
pi**2/6

A divergent sum or a nonexistent limit refuses with a readable error instead of returning a symbolic echo.

Optimization: Newton and BFGS where gradient descent stalls

min / min_nd default to plain gradient descent; method newton|bfgs switches to second-order methods with Armijo backtracking line search. On the Rosenbrock valley (start (-1.2, 1)) gradient descent refuses after 10 000 iterations, while BFGS converges in 36:

$ python -m pycodemath "min_nd (1-x)^2 + 100*(y-x^2)^2 for x,y at -1.2,1 method bfgs"
x = 0.999999999999454, y = 0.9999999999989762

ODE suite

Symbolic (dsolve) plus a full numerical toolbox — scalar and systems, forward and backward in time (t1 < t0), all refusing to silently jump over singularities (a readable error instead of garbage):

solver	what it does
solve_ode_num	classic fixed-step RK4
solve_ode_adaptive	Dormand–Prince 5(4), adaptive step (like ode45)
solve_ode_dense	adaptive + dense output: callable sol(t) anywhere
solve_ode_events	event detection g(t,y)=0 (+ terminal events)
solve_ode_stiff	implicit BDF2 + Newton for stiff equations
solve_ode_stiff_adaptive	variable-step BDF2 with local error control
solve_ode_system_*	vector variants of all of the above

Adaptive integration of a smooth problem takes 41 steps at rtol 1e-8:

$ python -m pycodemath "ode_adaptive y*cos(t) for y(t) from 0 to 5 at 1 rtol 1e-8"
y(5) = 0.3833049965035854  (41 adaptive steps)

On the stiff classic y' = -1000(y - cos t) the explicit pair is limited by stability (378 steps at rtol 1e-6; with the same budget fixed-step RK4 returns astronomically wrong finite values). The adaptive BDF gets there in 313 steps — and starting on the slow manifold, where stiffness is pure, in 58 steps vs 357:

$ python -m pycodemath "odestiff_adaptive -1000*(y-cos(t)) for y(t) from 0 to 1 at 0"
y(1) = 0.5411432587540607  (adaptive BDF, 313 implicit steps)

The system variant handles the Van der Pol oscillator with μ=1000 over [0, 2000] in 5 332 steps (~1 s) — an explicit method would need ≥ 2 000 000.

Code generation

code <expr> emits standalone, CSE-optimized NumPy source (real output):

$ python -m pycodemath "code (sin(x)+cos(x))^2 + (sin(x)+cos(x))^3"
import numpy as np


def f(x):
    """Pycodemath: f(x) — NumPy code."""
    _c0 = np.sin(x + (1/4)*np.pi)
    return 2*_c0**2*(np.sqrt(2)*_c0 + 1)

The Python API also generates standalone ODE integrators — including an adaptive one and one with dense output whose emitted interpolant is bit-for-bit identical to the engine (measured max difference: 0.0 on nodes and off-node grids, forward and backward):

from pycodemath import parse, generate_ode_dense

art = generate_ode_dense(parse("y*cos(t)"), "t", "y")
sol = art(1.0, 0.0, 5.0, 1e-8)   # standalone DOPRI5, returns an interpolant
sol(2.5)                          # -> 1.8193369962907706
len(sol.ts)                       # -> 42 accepted nodes

Event detection from the API:

from pycodemath import parse, solve_ode_events

ev = solve_ode_events(parse("cos(t)"), "t", 0.0, (0.0, 10.0), parse("y"), rtol=1e-8)
ev.event_times   # -> [3.141593, 6.283185, 9.424778]   (π, 2π, 3π)

Design contracts

• One IR (Expr/Matrix) shared by the engine and the generator.
• Numerical loops run on compiled functions (lambdify + LRU cache) — zero SymPy calls per iteration.
• Divergence or a domain problem raises a readable PycodemathError — never NaN/garbage in a result.
• The parser resolves only a whitelist of mathematical functions — unknown names become symbols, not Python code; string literals and attribute access are rejected outright, and evaluation cost is bounded so a single expression (e.g. 9**9**9) can't exhaust memory.
• Tests measure real numbers first, then assert them with a margin — 230 tests, all green, on Ubuntu and Windows (CI + mypy included).

License

MIT — see LICENSE.