Nuitka Release 0.5.27

This is to inform you about the new stable release of Nuitka. It is the extremely compatible Python compiler. Please see the page "What is Nuitka?" for an overview.

This release comes a lot of bug fixes and improvements.

Bug Fixes

  • Fix, need to add recursed modules immediately to the working set, or else they might first be processed in second pass, where global names that are locally assigned, are optimized to the built-in names although that should not happen. Fixed in already.
  • Fix, the accelerated call of methods could crash for some special types. This had been a regress of 0.5.25, but only happens with custom extension types. Fixed in already.
  • Python3.5: For async def functions parameter variables could fail to properly work with in-place assignments to them. Fixed in already.
  • Compatability: Decorators that overload type checks didn't pass the checks for compiled types. Now isinstance and as a result inspect module work fine for them.
  • Compatiblity: Fix, imports from __init__ were crashing the compiler. You are not supposed to do them, because they duplicate the package code, but they work.
  • Compatiblity: Fix, the super built-in on module level was crashing the compiler.
  • Standalone: For Linux, BSD and MacOS extension modules and shared libraries using their own $ORIGIN to find loaded DLLs resulted in those not being included in the distribution.
  • Standalone: Added more missing implicit dependencies.
  • Standalone: Fix, implicit imports now also can be optional, as e.g. _tkinter if not installed. Only include those if available.
  • The --recompile-c-only was only working with C compiler as a backend, but not in the C++ compatibility fallback, where files get renamed. This prevented that edit and test debug approach with at least MSVC.
  • Plugins: The PyLint plug-in didn't consider the symbolic name import-error but only the code F0401.
  • Implicit exception raises in conditional expressions would crash the compiler.

New Features

  • Added support for Visual Studio 2017. Issue#368.
  • Added option --python2-for-scons to specify the Python2 execute to use for calling Scons. This should allow using AnaConda Python for that task.


  • References to known unassigned variables are now statically optimized to exception raises and warned about if the according option is enabled.
  • Unhashable keys in dictionaries are now statically optimized to exception raises and warned about if the according option is enabled.
  • Enable forward propagation for classes too, resulting in some classes to create only static dictionaries. Currently this never happens for Python3, but it will, once we can statically optimize __prepare__ too.
  • Enable inlining of class dictionary creations if they are mere return statements of the created dictionary. Currently this never happens for Python3, see above for why.
  • Python2: Selecting the metaclass is now visible in the tree and can be statically optimized.
  • For executables, we now also use a freelist for traceback objects, which also makes exception cases slightly faster.
  • Generator expressions no longer require the use of a function call with a .0 argument value to carry the iterator value, instead their creation is directly inlined.
  • Remove "pass through" frames for Python2 list contractions, they are no longer needed. Minimal gain for generated code, but more lightweight at compile time.
  • When compiling Windows x64 with MinGW64 a link library needs to be created for linking against the Python DLL. This one is now cached and re-used if already done.
  • Use common code for NameError and UnboundLocalError exception code raises. In some cases it was creating the full string at compile time, in others at run time. Since the later is more efficient in terms of code size, we now use that everywhere, saving a bit of binary size.
  • Make sure to release unused functions from a module. This saves memory and can be decided after a full pass.
  • Avoid using OrderedDict in a couple of places, where they are not needed, but can be replaced with a later sorting, e.g. temporary variables by name, to achieve deterministic output. This saves memory at compile time.
  • Add specialized return nodes for the most frequent constant values, which are None, True, and False. Also a general one, for constant value return, which avoids the constant references. This saves quite a bit of memory and makes traversal of the tree a lot faster, due to not having any child nodes for the new forms of return statements.
  • Previously the empty dictionary constant reference was specialized to save memory. Now we also specialize empty set, list, and tuple constants to the same end. Also the hack to make is not say that {} is {} was made more general, mutable constant references and now known to never alias.
  • The source references can be marked internal, which means that they should never be visible to the user, but that was tracked as a flag to each of the many source references attached to each node in the tree. Making a special class for internal references avoids storing this in the object, but instead it's now a class property.
  • The nodes for named variable reference, assignment, and deletion got split into separate nodes, one to be used before the actual variable can be determined during tree building, and one for use later on. This makes their API clearer and saves a tiny bit of memory at compile time.
  • Also eliminated target variable references, which were pseudo children of assignments and deletion nodes for variable names, that didn't really do much, but consume processing time and memory.
  • Added optimization for calls to staticmethod and classmethod built-in methods along with type shapes.
  • Added optimization for open built-in on Python3, also adding the type shape file for the result.
  • Added optimization for bytearray built-in and constant values. These mutable constants can now be compile time computed as well.
  • Added optimization for frozenset built-in and constant values. These mutable constants can now be compile time computed as well.
  • Added optimization for divmod built-in.
  • Treat all built-in constant types, e.g. type itself as a constant. So far we did this only for constant values types, but of course this applies to all types, giving slightly more compact code for their uses.
  • Detect static raises if iterating over non-iterables and warn about them if the option is enabled.
  • Split of locals node into different types, one which needs the updated value, and one which just makes a copy. Properly track if a functions needs an updated locals dict, and if it doesn't, don't use that. This gives more efficient code for Python2 classes, and exec using functions in Python2.
  • Build all constant values without use of the pickle module which has a lot more overhead than marshal, instead use that for too large long values, non-UTF8 unicode values, nan float, etc.
  • Detect the linker arch for all Linux platforms using objdump instead of only a hand few hard coded ones.


  • The use of INCREASE_REFCOUNT got fully eliminated.
  • Use functions not vulenerable for buffer overflow. This is generally good and avoids warnings given on OpenBSD during linking.
  • Variable closure for classes is different from all functions, don't handle the difference in the base class, but for class nodes only.
  • Make sure mayBeNon doesn't return None which means normally "unclear", but False instead, since it's always clear for those cases.
  • Comparison nodes were using the general comparison node as a base class, but now a proper base class was added instead, allowing for cleaner code.
  • Valgrind test runners got changed to using proper tool namespace for their code and share it.
  • Made construct case generation code common testing code for re-use in the speedcenter web site. The code also has minor beauty bugs which will then become fixable.
  • Use appdirs package to determine place to store the downloaded copy of depends.exe.
  • The code still mentioned C++ in a lot of places, in comments or identifiers, which might be confusing readers of the code.
  • Code objects now carry all information necessary for their creation, and no longer need to access their parent to determine flag values. That parent is subject to change in the future.
  • Our import sorting wrapper automatically detects imports that could be local and makes them so, removing a few existing ones and preventing further ones on the future.
  • Cleanups and annotations to become Python3 PyLint clean as well. This found e.g. that source code references only had __cmp__ and need rich comparison to be fully portable.


  • The test runner for construct tests got cleaned up and the constructs now avoid using xrange so as to not need conversion for Python3 execution as much.
  • The main test runner got cleaned up and uses common code making it more versatile and robust.
  • Do not run test in debugger if CPython also segfaulted executing the test, then it's not a Nuitka issue, so we can ignore that.
  • Improve the way the Python to test with is found in the main test runner, prefer the running interpreter, then PATH and registry on Windows, this will find the interesting version more often.
  • Added support for "" to ignore the inline copies of code, they are not under our control.
  • The test runner for Valgrind got merged with the usage for constructs and uses common code now.
  • Construct generation is now common code, intended for sharing it with the Speedcenter web site generation.
  • Rebased Python 3.6 test suite to 3.6.1 as that is the Python generally used now.


  • Added inline copy of appdirs package from PyPI.
  • Added credits for RedBaron and isort.
  • The --experimental flag is now creating a list of indications and more than one can be used that way.
  • The PyLint runner can also work with Python3 pylint.
  • The Nuitka Speedcenter got more fine tuning and produces more tags to more easily identify trends in results. This needs to become more visible though.
  • The MSI files are also built on AppVeyor, where their building will not depend on me booting Windows. Getting these artifacts as downloads will be the next step.


This release improves many areas. The variable closure taking is now fully transparent due to different node types, the memory usage dropped again, a few obvious missing static optimizations were added, and many built-ins were completed.

This release again improves the scalability of Nuitka, which again uses less memory than before, although not an as big jump as before.

This does not extend or use special C code generation for bool or any type yet, which still needs design decisions to proceed and will come in a later release.


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