kalix 0.3.5

Python interface for Kalix: hydrological modelling and Pixie (Gorilla-compressed) timeseries I/O

kalix (Python)

Python interface for Kalix.

Current functionality:

• run simulations from INI model files (in-process, no separate CLI binary)
• run parameter optimisations from config files (in-process)
• read and write Pixie files (.pxt, .pxb)

Planned:

• programmatic model manipulation and building (a stateful Model class)
• richer optimisation control (progress callbacks, in-memory configs)

Design

The package binds the Rust engine directly via PyO3 rather than driving the engine's stdio session protocol (which exists to serve KalixIDE). This keeps the Python surface free to grow in whatever direction suits Python workflows, independent of the GUI's needs.

The current functions are deliberately stateless and mirror the two main CLI subcommands — simulate and optimise — so that moving from the command line to Python feels the same: point at files, get results back. A stateful Model object (load → mutate → run → inspect, all in memory) is the natural next layer and is planned, but the file-to-result convenience functions are expected to remain useful indefinitely.

Install

pip install kalix

Usage

Run a simulation

import kalix

kalix.simulate("model.ini", output_file="results.pxb")
df = kalix.read_pixie("results.pxb")
print(df.head())

The Python equivalent of kalix sim model.ini -o results.pxb, but in-process — no separate CLI binary required. Output format is inferred from the extension (.pxb for the Pixie pair, .csv for CSV).

Both outputs are keyword-only, and at least one is required:

# Outputs + mass-balance report
kalix.simulate("model.ini", output_file="results.pxb", mass_balance="mb.txt")

# Mass-balance only
kalix.simulate("model.ini", mass_balance="mb.txt")

Run an optimisation

import kalix

result = kalix.optimise("calibration.ini", model_file="initial_model.ini", save_model="final_model.ini")

print(result["best_objective"])      # lower is better
print(result["parameters"])          # {"node.my_sac.uzfwm": 42.7, ...}
print(result["optimised_model_ini"]) # string copy of the final model ini

The Python equivalent of kalix optimise calibration.ini, but in-process. The config .ini defines the algorithm, calibration terms, objective expression, parameter bounds, and termination criteria. Unlike simulate, optimise returns a result dictionary:

key	meaning
best_objective	best objective value found (lower is better)
n_evaluations	number of function evaluations performed
success	whether the optimiser terminated successfully
message	the optimiser's termination message
parameters	optimised parameters as {target: physical_value}
optimised_model_ini	the optimised model serialised back to an INI string

Two keyword-only options mirror the CLI's flags:

# Override the config's model_file (CLI: positional [model_file])
kalix.optimise("calibration.ini", model_file="other_model.ini")

# Also write the optimised model to disk (CLI: -s/--save-model)
kalix.optimise("calibration.ini", save_model="tuned.ini")

Paths inside the config (model_file, each term's observed_file) are resolved relative to the current working directory, exactly as the CLI does. If the config specifies an output_file, a results summary is written there too.

Read / write Pixie files

df = kalix.read_pixie("results.pxb")
print(df.head())

kalix.write_pixie("out.pxb", df)

The DataFrame index is a UTC DatetimeIndex; each column is one timeseries.

read_pixie accepts either extension (or no extension) and finds both files:

kalix.read_pixie("results.pxb")  # same as
kalix.read_pixie("results.pxt")  # same as
kalix.read_pixie("results")

write_pixie prefers a tz-aware DatetimeIndex, but will try to coerce other inputs (emitting a UserWarning when it does):

• a naive DatetimeIndex is localised to UTC;
• a default RangeIndex(0, n, 1) triggers promotion of the zeroth column to the index (and drops it from the body);
• any other non-DatetimeIndex is passed through pd.to_datetime(..., utc=True).

Integer and float dtypes are never auto-interpreted as datetimes (this would silently misread values as epoch nanoseconds). Set a DatetimeIndex explicitly in those cases.

Building from source

Requires Rust (1.70+) and maturin.

# Editable install for development
cd python
maturin develop --release
# uv run maturin develop --release --uv

# Build a wheel
maturin build --release
# uv run maturin build --release -- uv

Tests

Running tests directly

maturin develop
pytest python/tests

Alternatively with uv:

uv run maturin develop --uv
uv run pytest

Running tests with tox

Tox is configured to test against multiple Python versions (3.9-3.14):

# Run tests in development environment (fast, uses current Python)
uv run tox -e dev

# Run tests against all configured Python versions
uv run tox

# Run tests for specific Python version
uv run tox -e py312

# List all available test environments
uv run tox list

# Run tests in parallel
uv run tox -p auto