FAQs

Building on other platforms

NSIS can run on Linux, so you can build Windows installers without running Windows. However, if your package relies on compiled extension modules, like PyQt4, lxml or numpy, you’ll need to ensure that the installer is built with Windows versions of these packages. There are two ways to do this:

  • Get the importable packages/modules, either from a Windows installation, or by extracting them from an installer. Copy them into a folder called pynsist_pkgs, next to your installer.cfg file. pynsist will copy everything in this folder to the build directory.
  • Include exe/msi installers for those modules, and modify the .nsi template to extract and run these during installation. This can make your installer bigger and slower, and it may create unwanted start menu shortcuts (e.g. PyQt4 does), so the first option is usually better. However, if the installer sets up other things on the system, you may need to do this.

When running on non-Windows systems, pynsis will bundle a 32-bit version of Python by default, though you can override this in the config file. Whichever method you use, compiled libraries must have the same bit-ness as the version of Python that’s installed.

Using data files

Applications often need data files along with their code. The easiest way to use data files with Pynsist is to store them in a Python package (a directory with a __init__.py file) you’re creating for your application. They will be copied automatically, and modules in that package can locate them using __file__ like this:

data_file_path = os.path.join(os.path.dirname(__file__), 'file.dat')

If you don’t want to put data files inside a Python package, you will need to list them in the files key of the [Include] section of the config file. Your code can find them relative to the location of the launch script running your application (sys.modules['__main__'].__file__).

Code signing

People trying to use your installer will see an ‘Unknown publisher’ warning. To avoid this, you can sign it with a digital certificate. See Mozilla’s instructions on signing executables using Mono.

Signing requires a certificate from a trusted provider. These typically cost hundreds of dollars, but Certum offers a certificate for open source projects for €14 at the time of writing. You will need documents to prove your identity. I haven’t used a Certum certificate, and this isn’t an endorsement.

Alternatives

Other ways to distribute applications to users without Python installed include freeze tools, like cx_Freeze and PyInstaller, and Python compilers like Nuitka.

pynsist has some advantages:

  • Python code often does things—like using __file__ to find its location on disk, or sys.executable to launch Python processes—which don’t work when it’s run from a frozen exe. pynsist just installs Python files, so it avoids all these problems.
  • It’s quite easy to make Windows installers on other platforms, which is difficult with other tools.
  • The tool itself is simpler to understand, and less likely to need updating for new Python versions.

And some disadvantages:

  • Installers tend to be bigger because you’re bundling the whole Python standard library.
  • You don’t get an exe for your application, just a start menu shortcut to launch it.
  • pynsist only makes Windows installers.

Popular freeze tools also try to automatically detect what packages you’re using. Pynsist could do the same thing, but in my experience, this detection is complex and often misses things, so for now it expects an explicit list of the packages your application needs.

Another alternative is conda constructor, which builds an installer out of conda packages. Conda packages are more flexible than PyPI packages, and many libraries are already packaged, but you have to make a conda package of your own code as well before using conda constructor to make an installer. Conda constructor can also make Linux and Mac installers, but unlike Pynsist, it can’t make a Windows installer from Linux or Mac.