(transferred) [python-package] how to install the Python package from source? about lightgbm

[jameslamb]

@NigamSomya To install the Python package from a local copy of LightGBM, run the following:

sh build-python.sh install

For details on how to customize that, follow the docs at https://github.com/microsoft/LightGBM/blob/master/python-package/README.rst. You can ask here if you have other questions or concerns.

[NigamSomya]

Hi! Thanks that worked successfully, but it installed the package in this directory C:\Users\snigam\AppData\AppData2\Lib\site-packages\lightgbm\ which is not picking up the changes that I made to the dcg_calculator.cpp

Plus, when I cloned the source code in a different directory, I expected the command that you shared would install the necessary files in that directory only. Please help.

[jameslamb]

which is not picking up the changes that I made to the dcg_calculator.cpp

What evidence do you see the the changes you've made to LightGBM's source code are not being picked up in the Python package?

Just to be sure you understand...the Python package will not contain any .h or .cpp files. Those files are compiled into a shared library, lib_lightgbm.dll, that the Python package code calls.

If you run the command I show you from the root of the same repo where you changed any .cpp files in LightGBM, the resulting Python package will reflect your changes. Be sure you're doing that.

I expected the command that you shared would install the necessary files in that directory only.

The command I shared will build the lightgbm Python package and install it to where pip install on your system places packages by default.

If you want to control that more tightly, omit the install.

sh build-python.sh bdist_wheel

That will create a file with a name like lightgbm-4.3.0.99-py3-none-win_amd64.whl in the dist/ directory at the root of the LightGBM repo. That file is a Python wheel and you can install it to wherever you want.

[NigamSomya]

Hi!
Because I am getting the same error (kMaxposition error), I also ran the command in the same directory where my source code is place but somehow it gets installed as if I am running the usual pip command to install the lightgbm (in the usual appdata directory).

Also, the same thing happened when I tried to use this command sh build-python.sh bdist_wheel. Couldn't find anything named lightgbm-4.3.0.99-py3-none-win_amd64.whl. Must have been installed in the default directory and it behaves like the usual lightgbm package.
I am not sure what I am doing wrong, can you please help me with this?

[jameslamb]

somehow it gets installed as if I am running the usual pip command to install the lightgbm (in the usual appdata directory).

LightGBM's Python package does not support editable installs.

This command builds a wheel and installs it with pip install:

sh build-python.sh bdist_wheel install

This command builds a wheel and places it in the directory ./dist, relative to the root of the repo:

sh build-python.sh bdist_wheel

And then you are free to install it however you'd install other Python wheels. For example, like this:

pip install --no-deps ./dist/lightgbm-4.3.0.99-py3-none-win_amd64.whl

Because I am getting the same error (kMaxposition error)

To help you, we need more information than what you've provided.

• what version of LightGBM? (output of git log -n 2)
• what version of Python?
• can you share all of the build and installation logs?

Some things to try:

• be sure you save the file dcg_calculator.cpp before compiling
• be sure the Python interpreter used wherever you're running your program is the same one that was active from wherever you installed LightGBM
  • for example, if you are running your training code in a separate environment managed by venv / conda / poetry, then you need to install lightgbm into that environment
  • for example, if you are using a Jupyter notebook or similar, you may need to restart the kernel