impuls 1.1.2

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Impuls

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Impuls is a framework for processing static public transportation data. The internal model used is very close to GTFS.

The core entity for processing is called a pipeline, which is composed of multiple tasks that do the actual processing work.

The data is stored in an sqlite3 database with a very lightweight wrapper to map Impuls's internal model into SQL and GTFS.

Impuls has first-class support for pulling in data from external sources, using its resource mechanism. Resources are cached before the data is processed, which saves bandwidth if some of the input data has not changed, or even allows to stop the processing early if none of the resources have been modified.

A module for dealing with versioned, or multi-file sources is also provided. It allows for easy and very flexible processing of schedules provided in discrete versions into a single coherent file.

Installation and compilation

Impuls is mainly written in python, however a performance-critical part of this library is written in zig and bundled alongside the shared library. To compile and install the library, first ensure that zig is installed, then run the following, preferably inside of a virtual environment:

Impuls is mainly written in python, however a performance-critical part of this library is written in zig and bundled alongside the shared library. To install the library run the following, preferably inside of a virtual environment:

pip install impuls

Pre-built binaries are available for most platforms. To build from source zig needs to be installed.

The LoadBusManMDB task additionally requires mdbtools to be installed. This package is available in most package managers.

Examples

See https://impuls.readthedocs.io/en/stable/example.html for a tutorial and a more detailed walkthrough over Impuls features.

The examples directory contains 4 example configurations, processing data from four sources into a GTFS file. If you wish to run them, consult with the Development section of the readme to set up the environment correctly.

Kraków

Kraków provides decent GTFS files on https://gtfs.ztp.krakow.pl. The example pipeline removes unnecessary, confusing trip data and fixes several user-facing strings.

Run with python -m examples.krakow tram or python -m examples.krakow bus. The result GTFS will be created in _workspace_krakow/krakow.tram.out.zip or _workspace_krakow/krakow.bus.out.zip, accordingly.

PKP IC (PKP Intercity)

PKP Intercity provides their schedules in a single CSV table at ftp://ftps.intercity.pl. Unfortunately, the source data is not openly available. One needs to email PKP Intercity through the contact provided in the Polish MMTIS NAP in order to get the credentials.

The Pipeline starts by manually creating an Agency, loading the CSV data, pulling station data from https://github.com/MKuranowski/PLRailMap, adjusting some user-facing data - most importantly extracting trip legs operated by buses.

Run with python -m examples.pkpic FTP_USERNAME FTP_PASSWORD. The result GTFS will be created at _workspace_pkpic/pkpic.zip

Radom

MZDiK Radom provides schedules in a MDB database at http://mzdik.pl/index.php?id=145. It is the first example to use the multi-file pipeline support, as the source files are published in discrete versions.

Multi-file pipelines consist of four distinct parts:

• an intermediate provider, which figures out the relevant input ("intermediate") feeds
• a intermediate tasks factory, which returns the tasks necessary to load an intermediate feed into the SQLite database
• a final tasks factory, which returns the tasks to perform after merging intermediate feeds
• any additional resources, required by the intermediate or final tasks

Caching is even more involved - not only the input feeds are kept across runs, but the databases resulting from running intermediate pipelines are also preserved. If 3 of 4 feeds requested by the intermediate provider have already been processed - the intermediate pipeline will run only for the single new file, but the final (merging) pipeline will be run on all of the 4 feeds.

The intermediate provider for Radom scrapes the aforementioned website to find available databases.

Pipeline for processing intermediate feeds is a bit more complex: it involved loading the MDB database, cleaning up the data (removing virtual stops, generating and cleaning calendars) and pulling stop positions from http://rkm.mzdik.radom.pl/.

The final pipeline simply dumps the merged dataset into a GTFS.

Run with python -m examples.radom, the result GTFS will be created at _workspace_radom/radom.zip.

Warsaw

Warsaw is another city which requires multi-file pipelines. ZTM Warsaw publishes distinct input files for pretty much every other day at ftp://rozklady.ztm.waw.pl. The input datasets are in a completely custom text format, requiring quite involved parsing. More details are available at https://www.ztm.waw.pl/pliki-do-pobrania/dane-rozkladowe/ (in Polish).

The intermediate provider picks out relevant files from the aforementioned FTP server.

Processing of intermediate feeds starts with the import of the text file into the database. Rather uniquely, this step also prettifies stop names - as this would be hard to do in a separate task, due to the presence of indicators (two-digit codes uniquely identifying a stop around an intersection) in the name field. The pipeline continues by adding version meta-data, merging railway stations into a single stops.txt entry (ZTM separates railway departures into virtual stops) and attribute prettifying (namely trip_headsign and stop_lat,stop_lon - not all stops have positions in the input file). Last steps involve cleaning up unused entities from the database.

The final pipeline simply dumps the merged dataset into a GTFS, yet again.

Additional data for stop positions and edge-cases for prettifying stop names comes from https://github.com/MKuranowski/WarsawGTFS/blob/master/data_curated/stop_names.json.

Run with python -m examples.warsaw, the result GTFS will be created at _workspace_warsaw/warsaw.zip.

License

Impuls is distributed under GNU GPL v3 (or any later version).

© Copyright 2022-2024 Mikołaj Kuranowski

Impuls is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3 of the License, or (at your option) any later version.

Impuls is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with Impuls. If not, see http://www.gnu.org/licenses/.

Impuls source code and pre-built binaries come with sqlite3, which is placed in the public domain.

Development

Impuls uses meson-python. The project layout is quite unorthodox, as Impuls in neither a pure-python module, nor a project with a bog-standard C/C++ extension. Instead, the zig code is compiled into a shared library which is bundled alongside the python module.

Zig allows super easy cross-compilation, while using a shared library allows a single wheel to be used across multiple python versions and implementations.

Development requires python, zig and mdbtools (usually all 3 will be available in your package manager repositories) to be installed. To set up the environment on Linux, run:

$ python -m venv --upgrade-deps .venv
$ . .venv/bin/activate
$ pip install -Ur requirements.dev.txt
$ pip install --no-build-isolation -Cbuild-dir=builddir --editable .
$ ln -s ../../builddir/libextern.so impuls/extern

On MacOS, change the shared library file extension to .dylib. On Windows, change the extension of the shared library to .dll.

To run python tests, simply execute pytest. To run zig tests, run meson test -C builddir.

To run the examples, install their dependencies first (pip install -Ur requirements.examples.txt), then execute the example module, e.g. python -m examples.krakow.

meson-python will automatically recompile the zig library whenever an editable impuls install is imported; set the MESONPY_EDITABLE_VERBOSE environment variable to 1 to see meson logs for build details.

By default, the extern zig library will be built in debug mode. To change that, run meson configure --buildtype=debugoptimized builddir (buildtype can also be set to debug or release). To recompile the library, run meson compile -C builddir.

Unfortunately, meson-python requires all python and zig source files in meson.build. Python files need to be listed for packaging to work, while zig source files need to be listed for the build backend to properly detect whether libextern needs to be recompiled.

Building wheels

Zig has been chosen for its excellent cross-compilation support. Thanks to this, building all wheels for a release does not require tools like cibuildwheel, virtual machines, or even any containers. As long as Zig is installed, all wheels can be build on that machine.

Before building wheels, install a few extra dependencies in the virtual environment: pip install -U build wheel.

To build the wheels, simply run python build_wheels.py.

See python build_wheels.py --help for all available options. To debug failed builds, run python build_wheels.py --verbose --jobs 1 FAILED_CONFIG_NAME.

See CONFIGURATION in build_wheels.py for available configurations.

To build the source distribution, run python -m build -so dist.