Frequently Asked Questions

  • “Mach-O header may be too large to relocate”

    Py2app will fail with a relocation error when it cannot rewrite the load commands in shared libraries and binaries copied into the application or plugin bundle.

    This error can be avoided by rebuilding binaries with enough space in the Mach-O headers, either by using the linker flag “-headerpad_max_install_names” or by installing shared libraries in a deeply nested location (the path for the install root needs to be at least 30 characters long).

  • M1 Macs and libraries not available for arm64

    A lot of libraries are not yet available as arm64 or universal2 libraries.

    For applications using those libraries you can create an x86_64 (Intel) application instead:

    1. Create a new virtual environment and activate this

    2. Use arch -x86_64 python -mpip install ... to install libraries.

      The arch command is necessary here to ensure that pip selects variants that are compatible with the x86_64 architecture instead of arm64.

    3. Use arch -x86_64 python py2app --arch x86_64 to build

    This results in an application bundle where the launcher is an x86_64 only binary, and where included C extensions and libraries are compatible with that architecture as well.

  • Using Cython with py2app

    Cython generates C extensions. Because of that the dependency walker in py2app cannot find import statements in “.pyx” files”.

    To create working applications you have to ensure that dependencies are made visible to py2app, either by adding import statements to a python file that is included in the application, or by using the “includes” option.

    See examples/PyQt/cython_app in the repository for an example of the latter.

  • Dark mode support


    As of py2app 0.26 the stub executables are compiled with a modern SDK, with an automatic fallback to the older binaries for old builds of Tkinter.

    The stub executables from py2app were compiled on an old version of macOS and therefore the system assumes that applications build with py2app do not support Dark Mode unless you’re building a “Universal 2” or “Apple Silicon” application.

    To enable Dark Mode support for other builds of Python you need to add a key to the Info.plist file. The easiest way to do this is using the following option in