Nuitka Release 0.5.12

This is to inform you about the new stable release of Nuitka. It is the extremely compatible Python compiler, “download now”.

This release contains massive amounts of corrections for long standing issues in the import recursion mechanism, as well as for standalone issues now visible after the __file__ and __path__ values have changed to become runtime dependent values.

Bug Fixes

  • Fix, the __path__ attribute for packages was still the original filename’s directory, even in file reference mode was runtime.

  • The use of runtime as default file reference mode for executables, even if not in standalone mode, was making acceleration harder than necessary. Changed to original for that case. Fixed in already.

  • The constant value for the smallest int that is not yet a long is created using 1 due to C compiler limitations, but 1 was not yet initialized properly, if this was a global constant, i.e. used in multiple modules. Fixed in already.

  • Standalone: Recent fixes around __path__ revealed issues with PyWin32, where modules from were not properly recursed to. Fixed in already.

  • The importing of modules with the same name as a built-in module inside a package falsely assumed these were the built-ins which need not exist, and then didn’t recurse into them. This affected standalone mode the most, as the module was then missing entirely.

    # Inside "x.y" module:
    import x.y.exceptions
  • Similarly, the importing of modules with the same name as standard library modules could go wrong.

    # Inside "x.y" module:
    import x.y.types
  • Importing modules on Windows and macOS was not properly checking the checking the case, making it associate wrong modules from files with mismatching case.

  • Standalone: Importing with from __future__ import absolute_import would prefer relative imports still.

  • Python3: Code generation for try/return expr/finally could loose exceptions when expr raised an exception, leading to a RuntimeError for NULL return value. The real exception was lost.

  • Lambda expressions that were directly called with star arguments caused the compiler to crash.

    (lambda *args: args)(*args)  # was crashing Nuitka


  • Focusing on compile time memory usage, cyclic dependencies of trace merges that prevented them from being released, even when replaced were removed.

  • More memory efficient updating of global SSA traces, reducing memory usage during optimization by ca. 50%.

  • Code paths that cannot and therefore must not happen are now more clearly indicated to the backend compiler, allowing for slightly better code to be generated by it, as it can tell that certain code flows need not be merged.

New Features

  • Standalone: On systems, where .pth files inject Python packages at launch, these are now detected, and taking into account. Previously Nuitka did not recognize them, due to lack of files. These are mostly pip installations of e.g. zope.interface.

  • Added option --explain-imports to debug the import resolution code of Nuitka.

  • Added options --show-memory to display the amount of memory used in total and how it’s spread across the different node types during compilation.

  • The option --trace-execution now also covers early program initialisation before any Python code runs, to ease finding bugs in this domain as well.


  • Changed default for file reference mode to original unless standalone or module mode are used. For mere acceleration, breaking the reading of data files from __file__ is useless.

  • Added check that the in-line copy of scons is not run with Python3, which is not supported. Nuitka works fine with Python3, but a Python2 is required to execute scons.

  • Discover more kinds of Python2 installations on Linux/macOS installations.

  • Added instructions for macOS to the download page.


  • Moved oset and odict modules which provide ordered sets and dictionaries into a new package nuitka.container to clean up the top level scope.

  • Moved SyntaxErrors to nuitka.tree package, where it is used to format error messages.

  • Moved nuitka.Utils package to nuitka.utils.Utils creating a whole package for utils, so as to better structure them for their purpose.


This release is a major maintenance release. Support for namespace modules injected by *.pth is a major step for new compatibility. The import logic improvements expand the ability of standalone mode widely. Many more use cases will now work out of the box, and less errors will be found on case insensitive systems.

There is aside of memory issues, no new optimization though as many of these improvements could not be delivered as hotfixes (too invasive code changes), and should be out to the users as a stable release. Real optimization changes have been postponed to be next release.