Scenario 2 — Python package with multiple extensions¶

You're here if: you have several related but independent algorithms — Gain, EMA, Biquad — and you want them all in one package with separate .so files and full test coverage for each.

Multiple C objects in one project, all accessible from a single Python package.

1. Scaffold the first object¶

just-makeit new dsp_toolkit \
    --object gain \
    --arg-type float \
    --return-type float \
    --state gain:float:1.0
cd dsp_toolkit && make

2. Add a second object¶

just-makeit object ema \
    --arg-type float \
    --return-type float \
    --state alpha:double:0.1 \
    --state prev:float:0.0 \
    --mutable

object writes all C and Python files for the new standalone object and updates:

• root CMakeLists.txt — add_subdirectory + target_sources($<TARGET_OBJECTS:…>)
• umbrella header native/inc/dsp_toolkit.h — #include "ema/ema_core.h"
• src/dsp_toolkit/__init__.py — splices in from .ema import Ema and adds "Ema" to __all__, preserving any existing user edits

After adding ema, __init__.py looks like:

"""dsp_toolkit — Gain."""

from .gain import Gain
from .ema import Ema

__all__ = ["Gain", "Ema"]

No manual edits required.

3. Implement both objects¶

gain_step (read-only state):

static inline float
gain_step(const gain_state_t *state, float x)
{
    return state->gain * x;
}

ema_step (writes back to state — drop const):

static inline float
ema_step(ema_state_t *state, float x)
{
    float y = (float)state->alpha * x
            + (float)(1.0 - state->alpha) * state->prev;
    state->prev = y;
    return y;
}

4. Build and test¶

make && make test

CTest runs test_gain_core and test_ema_core. pytest runs the full generated suite for both objects.

5. Install¶

pip install .

The wheel bundles all compiled DSOs (gain.cpython-*.so, ema.cpython-*.so, …) alongside the Python package.

6. Use from Python¶

import numpy as np
from dsp_toolkit import Gain, Ema

signal = np.ones(20, dtype=np.float32)

gain = Gain(gain=2.0)
ema  = Ema(alpha=0.3)

for x in signal:
    y = ema.step(gain.step(x))

7. Add more objects¶

just-makeit object dc_block --state r:double:0.995

Each object repeats the same pattern: new C files, updated CMake, updated __init__.py. make picks up the new object automatically.

8. Install¶

pip install .

The wheel bundles the new DSO alongside all existing ones.