Building on other platforms

You can use Pynsist to build Windows installers from a Linux or Mac system. You’ll need to install NSIS so that the makensis command is available. Here’s how to do that on some common platforms:

  • Debian/Ubuntu: sudo apt-get install nsis

  • Fedora: sudo dnf install mingw32-nsis

  • Mac with Homebrew: brew install makensis

Installing Pynsist itself is the same on all platforms:

pip install pynsist

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 a few options for this:

  • List them under pypi_wheels in the Include section of your config file. Pynsist will download Windows-compatible wheels from PyPI. This is the easiest option if the dependency publishes wheels.

  • 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 it’s a last resort. However, if the installer sets up other things on the system, you may need to do this.

When running on non-Windows systems, Pynsist 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__).


The techniques above work for fixed data files which you ship with your application. For files which your app will write, you should use another location, because an app installed systemwide cannot write files in its install directory. Use the APPDATA or LOCALAPPDATA environment variables as locations to write hidden data files (what’s the difference?):

writable_file = os.path.join(os.environ['LOCALAPPDATA'], 'MyApp', 'file.dat')

Running subprocesses

There are a few things to be aware of if your code needs to run a subprocess:

  • The python command may not be found, or may be another version of Python. Use sys.executable to get the path of the Python executable running your application.

  • Commands which are normally installed by your Python dependencies, such as sphinx-build or pygmentize, won’t be available when your app is installed. You can often launch the same thing from an importable module by running something like {sys.executable} -m sphinx.

  • When your application runs as a GUI (without a console), subprocesses launched with sys.executable don’t have anywhere to write output. This makes debugging harder, and the subprocess can get stuck trying to write output. You can capture output in your code and print it (sending it to the log file described under Logging output):

    res = subprocess.run([sys.executable, "-c", "print('hello')"],
                         text=True, capture_output=True)

    If you want a console window to appear for your subprocess, check if sys.executable points to pythonw.exe, and use python.exe in the same folder instead:

    python = sys.executable
    if python.endswith('pythonw.exe'):
        python = python.removesuffix('pythonw.exe') + 'python.exe'
    subprocess.run([python, "-c", "print('hello'); input('Press enter')"])

    The console will close as soon as the subprocess finishes, so the example above uses input() to wait for input and give the user time to see it.

Bundling packages which don’t have wheels on PyPI

Most modern Python packages release packages in the ‘wheel’ format, which Pynsist can download and use automatically (pypi_wheels in the config file). But some older packages and packages with certain kinds of complexity don’t do this.

If you need to include a package which doesn’t release wheels, you can build your own wheels and include them with either the extra_wheel_sources or the local_wheels config options.

Run pip wheel package-name to build a wheel of a package on PyPI. If the package contains only Python code, this should always work.

If the package contains compiled extensions (typically C code), and does not publish wheels on PyPI, you will need to build the wheels on Windows, and you will need a suitable compiler installed. See Packaging binary extensions in the Python packaging user guide for more details. If you’re not familiar with building Python extension modules, this can be difficult, so you might want to think about whether you can solve the problem without that package.


If a package is maintained but doesn’t publish wheels, you could ask its maintainers to consider doing so. But be considerate! They may have reasons not to publish wheels, it may mean a lot of work for them, and they may have been asked before. Don’t assume that it’s their responsibility to build wheels, and do look for existing discussions on the topic before starting a new one.

Packaging with tkinter

Because Pynsist makes use of the “bundled” versions of Python the tkinter module isn’t included by default. If your application relies on tkinter for a GUI then you need to find the following assets:

  • The tcl directory in the root directory of a Windows installation of Python. This needs to come from the same Python version and bitness (i.e. 32-bit or 64-bit) as the Python you are bundling into the installer.

  • The _tkinter.pyd, tcl86t.dll and tk86t.dll libraries in the DLLs directory of the version of Python your are using in your app. As above, these must be the same bitness and version as your target version of Python.

  • The _tkinter.lib file in the libs directory of the version of Python you are using in your app. Same caveats as above.

The tcl directory should be copied into the root of your project (i.e. in the directory that contains installer.cfg) and renamed to lib (this is important!).

Create a new directory in the root of your project called pynsist_pkgs and copy over the other four files mentioned above into it (so it contains _tkinter.lib, _tkinter.pyd, tcl86t.dll and tk86t.dll).

Finally, in your .cfg file ensure the packages section contains tkinter and _tkinter, and the files section contains lib, like this:



Build your installer and test it. You’ll know everything is in the right place if the directory into which your application is installed contains a lib directory containing the contents of the original tcl directory and the pkgs directory contains the remaining four files. If things still don’t work check the bitness and Python version associated with these assets and make sure they’re the same as the version of Python installed with your application.


A future version of Pynsist might automate some of this procedure to make distributing tkinter applications easier.

DLL load failed errors

Importing compiled extension modules in your application may fail with errors like this:

ImportError: DLL load failed: The specified module could not be found.

This means that the Python module it’s trying to load needs a DLL which isn’t there. Unfortunately, the error message doesn’t say which DLL is missing, and there’s no simple way to identify it.

The traceback should show which import failed. The module that was being imported should be a file with a .pyd extension. You can use a program called Dependency Walker on this file to work out what DLLs it needs and which are missing, though you may need to adjust the ‘module search order’ to avoid some false negatives.

Once you’ve worked out what is missing, you’ll need to make it available. This may mean bundling extra DLLs as data files. If you do this, it’s up to you to ensure you have the right to redistribute them.

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, or this guide from Adafruit on signing an installer.

Signing requires a certificate from a provider trusted by Microsoft. As of summer 2017, these are the cheapest options I can find:

  • Certum’s open source code signing certificate: €86 for a certificate with a smart card and reader, €28 for a new certificate if you have the hardware. Each certificate is valid for one year. This is only for open source software.

  • Many companies resell Comodo code signing certificates at prices lower than Comodo themselves, especially if you pay for 3–4 years up front. CodeSignCert ($59–75 per year), K Software ($67–$84 per year) and Cheap SSL Security (UK, £54–£64 per year) are a few examples; a search will turn up many more like them.

I haven’t used any of these companies, so I’m not making a recommendation. Please do your own research before buying from them.

If you find another good way to get a code signing certificate, please make a pull request to add it!


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.