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LPython is an ahead-of-time compiler for Python written in C++. It is currently in alpha stage and under heavy development. LPython works on Windows, macOS and Linux.

Some of the goals of LPython include:

  • Providing the best possible performance for numerical and array-oriented code.
  • Ahead-of-Time, fast compilation to binaries, plus interactive usage (Jupyter notebook).
  • Cross-platform support.
  • Being able to compile a subset of Python yet be fully compatible with it.
  • Transforming Python code to other programming languages like C++ and Fortran.
  • Exploring design patterns so that LPython can eventually compile all Python code.
  • Providing excellent user-friendly diagnostic messages: error, warnings, hints, notes, etc.

among many more.


LPython has been sponsored by GSI Technology. Our summer students were sponsored by Google Summer of Code via Python Software Foundation. The intermediate representation and backends are shared with LFortran, see that project for a list of sponsors.


Follow the steps below to install and run LPython on Linux, Windows or macOS.


  • Install Conda

    Follow the instructions provided here to install Conda on your platform (Linux, macOS and Windows) using a conda-forge distribution called Miniforge.

    For Windows, these are additional requirements:

    • Miniforge Prompt
    • Visual Studio (with "Desktop Development with C++" workload)
  • Set up your system

    • Linux

      • Run the following command to install some global build dependencies:

        sudo apt-get install build-essential binutils-dev clang zlib1g-dev
    • Windows

      • Download and install Microsoft Visual Studio Community for free.

      • Run the Visual Studio Installer. Download and install the "Desktop Development with C++" workload which will install the Visual C++ Compiler (MSVC).

      • Launch the Miniforge prompt from the Desktop. It is recommended to use MiniForge instead of Powershell as the main terminal to build and write code for LPython. In the MiniForge Prompt, initialize the MSVC compiler using the below command:

        call "C:\Program Files\Microsoft Visual Studio\2022\Community\Common7\Tools\VsDevCmd" -arch=x64

        You can optionally test MSVC via:

        cl /?
        link /?

        Both commands must print several pages of help text.

    • Windows with WSL

      • Install Miniforge Prompt and add it to path:

        wget -O
        bash -b -p $HOME/conda_root
        export PATH="$HOME/conda_root/bin:$PATH"
        conda init bash # (shell name)
      • Open a new terminal window and run the following commands to install dependencies:

        conda create -n lp -c conda-forge llvmdev=11.0.1 bison=3.4 re2c python cmake make toml clangdev git
      • Optionally, you can change the directory to a Windows location using cd /mnt/[drive letter]/[windows location]. For e.g. - cd mnt/c/Users/name/source/repos/.

  • Clone the LPython repository

    Make sure you have git installed. Type the following command to clone the repository:

    git clone
    cd lpython

    You may also use GitHub Desktop to do the same.

Building LPython

  • Linux and macOS

    • Create a Conda environment:

      conda env create -f environment_unix.yml
      conda activate lp
    • Generate the prerequisite files and build in Debug Mode:

      # if you are developing on top of a forked repository; please run following command first
      # ./
  • Windows

    • Create a Conda environment using the pre-existing file:

      conda env create -f environment_win.yml
      conda activate lp
    • Generate the prerequisite files and build in Release Mode:

      call build0.bat
      call build1.bat
  • Windows with WSL

    • Activate the Conda environment:

      conda activate lp
    • Run the following commands to build the project:

      cmake -DCMAKE_BUILD_TYPE=Debug -DWITH_LLVM=yes -DCMAKE_INSTALL_PREFIX=`pwd`/inst .\
      make -j8

Check the installation-docs for more.


We welcome contributions from anyone, even if you are new to compilers or open source in general. It might sound daunting at first to contribute to a compiler, but do not worry, it is not that complicated. We will help you with any technical issues you face and provide support so your contribution gets merged.

To contribute, submit a Pull Request (PR) against our repository at:

Do not forget to clean your history, see example.

See the CONTRIBUTING document for more information.

Found a bug?

Please report any bugs you find at our issue tracker here. Or, even better, fork the repository on GitHub and create a Pull Request (PR).

We welcome all changes, big or small. We will help you make a PR if you are new to git.

If you have any questions or need help, please ask us at Zulip or on our mailinglist.

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