This document is the recommended first read if you are interested in using Nuitka, understand its use cases, check what you can expect, license, requirements, credits, etc.
Nuitka is the Python compiler. It is written in Python. It is a seamless replacement or extension to the Python interpreter and compiles every construct that CPython 2.6, 2.7, 3.3, 3.4, 3.5, 3.6, 3.7, and 3.8 have, when itself run with that Python version.
It then executes uncompiled code and compiled code together in an extremely compatible manner.
You can use all Python library modules and all extension modules freely.
Nuitka translates the Python modules into a C level program that then uses
libpython and static C files of its own to execute in the same way as
All optimization is aimed at avoiding overhead, where it's unnecessary. None is aimed at removing compatibility, although slight improvements will occasionally be done, where not every bug of standard Python is emulated, e.g. more complete error messages are given, but there is a full compatibility mode to disable even that.
C Compiler: You need a compiler with support for C11 or alternatively for C++03 1
Currently this means, you need to use one of these compilers:
gcccompiler of at least version 5.1, or the
g++compiler of at least version 4.4 as an alternative.
clangcompiler on macOS X or FreeBSD.
Visual Studio 2019 or higher on Windows 4, older versions may work but are not officially supported. Configure to use the English language pack for best results (Nuitka filters away garbage outputs, but only for that language).
On Windows the
clang-clcompiler on Windows can be used if provided if you use the
CCenvironment variable to point to it, and you also have MSVC installed.
Python: Version 2.6, 2.7 or 3.3, 3.4, 3.5, 3.6, 3.7, 3.8
For 3.3, and 3.4 and only those versions, we need other Python versions as a compile time dependency
Nuitka itself is fully compatible with all mentioned versions, Scons as an internally used tool is not.
For these versions, you need a Python2 or Python 3.5 or higher installed as well, but only during the compile time only. That is for use with Scons (which orchestrates the C compilation), which does not support the same Python versions as Nuitka.
Moving binaries to other machines
The created binaries can be made executable independent of the Python installation, with
Binary filename suffix
The created binaries have an
.exesuffix on Windows. On other platforms they have no suffix for standalone mode, or
.binsuffix, that you are free to remove or change, or specify with the
The suffix for acceleration mode is added just to be sure that the original script name and the binary name do not ever collide, so we can safely do an overwrite without destroying the original source file.
It has to be CPython, Anaconda or Miniconda Python.
You need the standard Python implementation, called "CPython", to execute Nuitka, because it is closely tied to implementation details of it.
On Windows, for Python not installed system-wide and acceleration mode, you need to copy the
PythonXX.DLLalongside it, something Nuitka does automatically.
It has to be CPython, AnaConda or MiniConda Python.
It is known that Windows app store Python definitely does not work, it's checked against. And on macOS "pyenv" likely does not work.
Operating System: Linux, FreeBSD, NetBSD, macOS X, and Windows (32/64 bits).
Others may work as well. The portability is expected to be generally good, but the e.g. Scons usage may have to be adapted. Make sure to match Windows Python and C compiler architecture, or else you will get cryptic error messages.
Architectures: x86, x86_64 (amd64), and arm, likely many more
Other architectures are expected to also work, out of the box, as Nuitka is generally not using any hardware specifics. These are just the ones tested and known to be good. Feedback is welcome. Generally, the architectures that Debian supports can be considered good and tested too.
Support for this C11 is a given with gcc 5 or higher or any clang version. The MSVC compiler doesn't do it yet. But as a workaround, as the C++03 language standard is very overlapping with C11, it is then used instead where the C compiler is too old. Nuitka used to require a C++ compiler in the past, but it changed.
Download MinGW64 from here http://mingw-w64.org/ and choose 64 or 32 bits matching your Python.
Use both MinGW64 and 64 bits Python if you have the choice of which Python to use. Install it to
\MinGW64(same disk root as Nuitka running) to find it automatically. Also, when prompted, use
posixfor threads and
dwarffor exception model, although these currently do not matter at all.
Installation of matching MinGW64 is easiest if you have an Anaconda or Miniconda installation.
<path_to_Anaconda>\Scripts\conda install m2w64-gcc libpythonand then before you run Nuitka do
setenv CC=<path_to_Anaconda>\Library\mingw-w64\bin\gcc.exeand then its use will be forced. Nuitka also uses it automatically, if you run it like this
<path_to_Anaconda>\python -m nuitka ....
Download for free from http://www.visualstudio.com/en-us/downloads/download-visual-studio-vs.aspx (the Express editions work just fine).
The latest version is recommended if not required. There is no need to use older versions, they might in fact not work.
The recommended way of executing Nuitka is
<the_right_python> -m nuitka to
be absolutely certain which Python interpreter you are using, so it is easier
to match with what Nuitka has.
The next best way of executing Nuitka bare that is from a source checkout or
archive, with no environment variable changes, most noteworthy, you do not
have to mess with
PYTHONPATH at all for Nuitka. You just execute the
nuitka-run scripts directly without any changes to the
environment. You may want to add the
bin directory to your
your convenience, but that step is optional.
Moreover, if you want to execute with the right interpreter, in that case, be
sure to execute
<the_right_python> bin/nuitka and be good.
Pick the right Interpreter
If you encounter a
SyntaxErroryou absolutely most certainly have picked the wrong interpreter for the program you are compiling.
Nuitka has a
--help option to output what it can do:
nuitka-run command is the same as
nuitka, but with a different
default. It tries to compile and directly execute a Python script:
This option that is different is
--run, and passing on arguments after the
first non-option to the created binary, so it is somewhat more similar to what
python will do.
For most systems, there will be packages on the download page of Nuitka. But you can also
install it from source code as described above, but also like any other Python
program it can be installed via the normal
python setup.py install routine.
Nuitka is licensed under the Apache License, Version 2.0; you may not use it except in compliance with the License.
You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.
This is basic steps if you have nothing installed, of course if you have any of the parts, just skip it.
Download and install mingw64 from https://sourceforge.net/projects/mingw-w64/
For Architecture: choose "i686" if you want use 32bit or "x86_64" if you want 64 bit version Python, otherwise you will get errors later
Select destination folder to
Verify using command
Set a environment variable pointing to
CC=C:\\MinGW64\\mingw64\\bin\\gcc.exeif 64 bit version
CC=C:\\MinGW64\\mingw32\\bin\\gcc.exeif 32 bit version
Download and install from https://www.python.org/downloads/windows
Select one of
Windows x86-64 web-based installeror
Verify using command
pip install nuitka
or if you use anaconda:
conda install -c conda-forge nuitka
Verify using command
python -m nuitka --standalone --mingw64 hello.py
If you like to have full output add --show-progress --show-scons
Execute the hello.exe in the folder hello.dist
To distribute copy the hello.dist folder
If you want to compile a whole program recursively, and not only the single file that is the main program, do it like this:
There are more fine grained controls than
Consider the output of
In case you have a plugin directory, i.e. one which cannot be found by
recursing after normal import statements via the
PYTHONPATH (which would be
the recommended way), you can always require that a given directory shall also
be included in the executable:
If you don't do any dynamic imports, simply setting your
compilation time will be sufficient for all your needs normally.
--include-plugin-directory only if you make
that Nuitka cannot predict, because they e.g. depend on command line
parameters. Nuitka also warns about these, and point to the option.
The resulting filename will be
program.exe on Windows,
on other platforms.
The resulting binary still depends on CPython and used C extension modules being installed.
If you want to be able to copy it to another machine, use
and copy the created
program.dist directory and execute the
program.exe (Windows) or
program (other platforms) put inside.
If you want to compile a single extension module, all you have to do is this:
The resulting file
some_module.so can then be used instead of
It's left as an exercise to the reader, to find out what happens if both are present.
--follow-imports and other variants work as well, but the
included modules will only become importable after you imported the
If you need to compile a whole package and embed all modules, that is also feasible, use Nuitka like this:
The recursion into the package directory needs to be provided manually, otherwise, the package is empty. Data files located inside the package will not be embedded yet.
If your script modifies
sys.path to e.g. insert directories with source
code relative to it, Nuitka will currently not be able to see those. However,
if you set the
PYTHONPATH to the resulting value, you will be able to
For passing things like
-S to your program, there is a command
line option name
--python-flag= which makes Nuitka emulate these options.
The most important ones are supported, more can certainly be added.
The C compiler, when invoked with the same input files, will take a long time
and much CPU to compile. Make sure you are having
ccache installed and
configured on non-Windows. It will make repeated compilations much faster,
even if things are not yet not perfect, i.e. changes to the program can
cause many C files to change, requiring a new compilation instead of using
the cached result.
On Windows, Nuitka supports using
ccache.exe which is not easy to come
by though for the non-MSVC compilers, and
clcache.exe which is just one
pip install clcache command away. To make Nuitka use those, set either
NUITKA_CCACHE_BINARY to the full path of
NUITKA_CLCACHE_BINARY to the full path of
clcache.exe, which will be
in the scripts folder of the Python, you installed it into.
Avoid running the
nuitka binary, doing
python -m nuitka will make a
100% sure you are using what you think you are.
The fastest binaries of
pystone.exe on Windows with 64 bits Python proved
to be significantly faster with MinGW64, roughly 20% better score. So it is
recommended for use over MSVC. Using
clang-cl.exe of Clang7 was faster
than MSVC, but still significantly slower than MinGW64, and it will be harder
to use, so it is not recommended.
On Linux for
pystone.bin the binary produced by
clang6 was faster
gcc-6.3, but not by a significant margin. Since gcc is more often
already installed, that is recommended to use for now.
Differences in C compilation times have not yet been examined.
Using the Python DLL, like standard CPython does can lead to unexpected slowdowns, e.g. in uncompiled code that works with Unicode strings. This is because calling to the DLL rather than residing in the DLL causes overhead, and this even happens to the DLL with itself, being slower, than a Python all contained in one binary.
So if feasible, aim at static linking, which is currently only possible with Anaconda Python on non-Windows.
The process of making standalone executables for Windows traditionally involves using an external dependency walker in order to copy necessary libraries along with the compiled executables to the distribution folder.
Using the external dependency walker is quite a time consuming, and may copy some unnecessary libraries along the way (better have too much than missing).
There's also an experimental alternative internal dependency walker that relies on pefile which analyses PE imports of executables and libraries.
This implementation shall create smaller Standalone distributions since it won't include Windows' equivalent of the standard library, and will speed-up first Nuitka compilations by an order of magnitude.
In order to use it, you may enable the internal dependency walker by using the following switch:
The pefile dependency walker will test all dependencies of the distribution folder.
Optionally, it is also possible to check all recursive dependencies of included libraries using the following switch along with the above one:
python -m nuitka --standalone --windows-dependency-tool=pefile --experimental=use_pefile_recurse myprogram.py
Some modules may have hidden dependencies outside of their directory. In order for the pefile dependency walker to find them, you may also scan the whole site-packages directory for missing dependencies using the following switch along with the two above:
python -m nuitka --standalone --windows-dependency-tool=pefile --experimental=use_pefile_recurse --experimental=use_pefile_fullrecurse myprogram.py
Be aware that using this switch will increase compilation time a lot.
Whether compiling with MingW or MSVC, the standalone programs have external dependencies to Visual C Runtime libraries. Nuitka tries to ship those dependent DLLs by copying them from your system.
Beginning with Microsoft Windows 10, Microsoft ships ucrt.dll (Universal C Runtime libraries) which rehook calls to api-ms-crt-*.dll.
With earlier Windows platforms (and wine/ReactOS), you should consider installing Visual C Runtime libraries before executing a Nuitka standalone compiled program.
Depdending on the used C compiler, you'll need the following redist versions:
Visual C version
3.5, 3.6, 3.7, 3.8
3.5, 3.6, 3.7, 3.8
3.5, 3.6, 3.7, 3.8
2.6, 2.7, 3.0, 3.1, 3.2
When using MingGW64, you'll need the following redist versions:
3.5, 3.6, 3.7, 3.8
Once the corresponding runtime libraries are installed on the target system, you may remove all api-ms-crt-*.dll files from your Nuitka compiled dist folder.
It doesn't set
sys.frozen unlike other tools. For Nuitka, we have the
__compiled__ to test if a specific module was compiled.
Remember, this project is not completed yet. Although the CPython test suite works near perfect, there is still more work needed, esp. to make it do more optimization. Try it out.
Nuitka announcements and interesting stuff is pointed to on the Twitter account, but obviously with no details. @KayHayen.
I will not answer Nuitka issues via Twitter though, rather make occasional polls, and give important announcements, as well as low-level posts about development ongoing.
Should you encounter any issues, bugs, or ideas, please visit the Nuitka bug tracker and report them.
Best practices for reporting bugs:
Please always include the following information in your report, for the underlying Python version. You can easily copy&paste this into your report.
Try to make your example minimal. That is, try to remove code that does not contribute to the issue as much as possible. Ideally come up with a small reproducing program that illustrates the issue, using
If the problem occurs spuriously (i.e. not each time), try to set the environment variable
0, disabling hash randomization. If that makes the problem go away, try increasing in steps of 1 to a hash seed value that makes it happen every time, include it in your report.
Do not include the created code in your report. Given proper input, it's redundant, and it's not likely that I will look at it without the ability to change the Python or Nuitka source and re-run it.
Do not send screenshots of text, that is bad and lazy. Instead, capture text outputs from the console.
Consider using this software with caution. Even though many tests are applied before releases, things are potentially breaking. Your feedback and patches to Nuitka are very welcome.
You are more than welcome to join Nuitka development and help to complete the project in all minor and major ways.
The development of Nuitka occurs in git. We currently have these 3 branches:
This branch contains the stable release to which only hotfixes for bugs will be done. It is supposed to work at all times and is supported.
This branch contains the ongoing development. It may at times contain little regressions, but also new features. On this branch, the integration work is done, whereas new features might be developed on feature branches.
This branch contains unfinished and incomplete work. It is very frequently subject to
git rebaseand the public staging ground, where my work for develop branch lives first. It is intended for testing only and recommended to base any of your own development on. When updating it, you very often will get merge conflicts. Simply resolve those by doing
git reset --hard origin/factoryand switch to the latest version.
I accept requests on the social code platforms, also patch files, if they are good.
The Developer Manual explains the coding rules, branching model used, with feature branches and hotfix releases, the Nuitka design and much more. Consider reading it to become a contributor. This document is intended for Nuitka users.
Should you feel that you cannot help Nuitka directly, but still want to support, please consider making a donation and help this way.
The code objects are empty for native compiled functions. There is no bytecode with Nuitka's compiled function objects, so there is no way to provide it.
There is no tracing of compiled functions to attach a debugger to.
The most important form of optimization is the constant folding. This is when an operation can be fully predicted at compile time. Currently, Nuitka does these for some built-ins (but not all yet, somebody to look at this more closely will be very welcome!), and it does it e.g. for binary/unary operations and comparisons.
Constants currently recognized:
Literals are the one obvious source of constants, but also most likely other optimization steps like constant propagation or function inlining will be. So this one should not be underestimated and a very important step of successful optimizations. Every option to produce a constant may impact the generated code quality a lot.
The folding of constants is considered implemented, but it might be incomplete in that not all possible cases are caught. Please report it as a bug when you find an operation in Nuitka that has only constants as input and is not folded.
At the core of optimizations, there is an attempt to determine the values of variables at run time and predictions of assignments. It determines if their inputs are constants or of similar values. An expression, e.g. a module variable access, an expensive operation, may be constant across the module of the function scope and then there needs to be none or no repeated module variable look-up.
Consider e.g. the module attribute
__name__ which likely is only ever read,
so its value could be predicted to a constant string known at compile time.
This can then be used as input to the constant folding.
From modules attributes, only
__name__ is currently actually optimized.
Also possible would be at least
__doc__. In the future, this may improve
as SSA is expanded to module variables.
Also, built-in exception name references are optimized if they are used as a module level read-only variables:
This works for all built-in names. When an assignment is done to such a name, or it's even local, then, of course, it is not done.
For built-in calls like
range it is often possible to
predict the result at compile time, esp. for constant inputs the resulting
value often can be precomputed by Nuitka. It can simply determine the result or
the raised exception and replace the built-in call with that value, allowing
for more constant folding or code path reduction.
type("string") # predictable result, builtin type str. len([1, 2]) # predictable result range(3, 9, 2) # predictable result range(3, 9, 0) # predictable exception, range raises due to 0.
The built-in call prediction is considered implemented. We can simply during compile time emulate the call and use its result or raised exception. But we may not cover all the built-ins there are yet.
Sometimes the result of a built-in should not be predicted when the result is
range() call e.g. may give too big values to include the result in
the binary. Then it is not done.
This is considered mostly implemented. Please file bugs for built-ins that are pre-computed, but should not be computed by Nuitka at compile time with specific values.
For conditional statements, some branches may not ever be taken, because of the conditions being possible to predict. In these cases, the branch not taken and the condition check is removed.
This can typically predict code like this:
It will also benefit from constant propagations, or enable them because once some branches have been removed, other things may become more predictable, so this can trigger other optimization to become possible.
Every branch removed makes optimization more likely. With some code branches removed, access patterns may be more friendly. Imagine e.g. that a function is only called in a removed branch. It may be possible to remove it entirely, and that may have other consequences too.
This is considered implemented, but for the maximum benefit, more constants need to be determined at compile time.
For exceptions that are determined at compile time, there is an expression that will simply do raise the exception. These can be propagated upwards, collecting potentially "side effects", i.e. parts of expressions that were executed before it occurred, and still have to be executed.
Consider the following code:
(1 / 0) can be predicted to raise a
which will be propagated through the
+ operation. That part is just
Constant Propagation as normal.
side_effect_having() will have to be retained though, but the
something_else call needs no
code generation or consideration anymore.
To that end, Nuitka works with a special node that raises an exception and is wrapped with a so-called "side_effects" expression, but yet can be used in the code as an expression having a value.
The propagation of exceptions is mostly implemented but needs handling in every kind of operations, and not all of them might do it already. As work progresses or examples arise, the coverage will be extended. Feel free to generate bug reports with non-working examples.
Consider the following code:
try block is bigger than it needs to be. The statement
b = 8 cannot
ValueError to be raised. As such it can be moved to outside the try
without any risk.
This is considered done. For every kind of operation, we trace if it may
raise an exception. We do however not track properly yet, what can do
ValueError and what cannot.
With the exception propagation, it then becomes possible to transform this code:
Which then can be lowered in complexity by avoiding the raise and catch of the exception, making it:
This is not implemented yet.
For loops and conditional statements that contain only code without effect, it should be possible to remove the whole construct:
The loop could be removed, at maximum, it should be considered an assignment of
999 and no more.
This is not implemented yet, as it requires us to track iterators, and their side effects, as well as loop values, and exit conditions. Too much yet, but we will get there.
The condition check should be removed in this case, as its evaluation is not
needed. It may be difficult to predict that
side_effect_free has no side
effects, but many times this might be possible.
This is considered implemented. The conditional statement nature is removed if both branches are empty, only the condition is evaluated and checked for truth (in cases that could raise an exception).
When the length of the right-hand side of an assignment to a sequence can be predicted, the unpacking can be replaced with multiple assignments.
This is of course only really safe if the left-hand side cannot raise an exception while building the assignment targets.
We do this now, but only for constants, because we currently have no ability to predict if an expression can raise an exception or not.
Not implemented yet. Will need us to see through the unpacking of what is an iteration over a tuple, we created ourselves. We are not there yet, but we will get there.
When a construct like
in xrange() or
in range() is used, it is possible
to know what the iteration does and represent that so that iterator users can
use that instead.
I consider that:
xrange(1000) into an object of a special class that does
the integer looping more efficiently. In case
i is only assigned from
there, this could be a nice case for a dedicated class.
Future work, not even started.
Functions are structured so that their parameter parsing and
interface is separate from the actual function code. This way the call can be
optimized away. One problem is that the evaluation order can differ.
This will have to evaluate first
get2() and only then
get3() and then make the function call with these values.
Therefore it will be necessary to have a staging of the parameters before
making the actual call, to avoid a re-ordering of the calls to
Not even started. A re-formulation that avoids the dictionary to call the function, and instead uses temporary variables appears to be relatively straight forward once we do that kind of parameter analysis.
In some cases, accesses to
list constants can become
Can be optimized into this:
This allows for simpler, faster code to be generated, and fewer checks needed,
because e.g. the
tuple is clearly immutable, whereas the
list needs a
check to assert that. This is also possible for sets.
Implemented, even works for non-constants. Needs other optimization to become generally useful, and will itself help other optimization to become possible. This allows us to e.g. only treat iteration over tuples, and not care about sets.
In theory, something similar is also possible for
dict. For the later, it
will be non-trivial though to maintain the order of execution without temporary
values introduced. The same thing is done for pure constants of these types,
they change to
tuple values when iterated.
Thanks go to these individuals for their much-valued contributions to Nuitka. Contributors have the license to use Nuitka for their own code even if Closed Source.
The order is sorted by time.
Li Xuan Ji: Contributed patches for general portability issue and enhancements to the environment variable settings.
Nicolas Dumazet: Found and fixed reference counting issues,
importpackages work, improved some of the English and generally made good code contributions all over the place, solved code generation TODOs, did tree building cleanups, core stuff.
Khalid Abu Bakr: Submitted patches for his work to support MinGW and Windows, debugged the issues, and helped me to get cross compile with MinGW from Linux to Windows. This was quite difficult stuff.
Liu Zhenhai: Submitted patches for Windows support, making the inline Scons copy actually work on Windows as well. Also reported import related bugs, and generally helped me make the Windows port more usable through his testing and information.
Christopher Tott: Submitted patches for Windows, and general as well as structural cleanups.
Pete Hunt: Submitted patches for macOS X support.
"ownssh": Submitted patches for built-ins module guarding, and made massive efforts to make high-quality bug reports. Also the initial "standalone" mode implementation was created by him.
"Dr. Equivalent": Submitted the Nuitka Logo.
Johan Holmberg: Submitted patch for Python3 support on macOS X.
Umbra: Submitted patches to make the Windows port more usable, adding user provided application icons, as well as MSVC support for large constants and console applications.
David Cortesi: Submitted patches and test cases to make macOS port more usable, specifically for the Python3 standalone support of Qt.
Andrew Leech: Submitted github pull request to allow using "-m nuitka" to call the compiler. Also pull request to improve "bist_nuitka" and to do the registration.
Paweł K: Submitted github pull request to remove glibc from standalone distribution, saving size and improving robustness considering the various distributions.
Orsiris de Jong: Submitted github pull request to implement the dependency walking with pefile under Windows.
Jorj X. McKie: Submitted github pull requests with NumPy plugin to retain its accelerating libraries, and Tkinter to include the TCL distribution on Windows.
The CPython project
Thanks for giving us CPython, which is the base of Nuitka. We are nothing without it.
The GCC project
Thanks for not only the best compiler suite but also thanks for making it easy supporting to get Nuitka off the ground. Your compiler was the first usable for Nuitka and with very little effort.
The Scons project
Thanks for tackling the difficult points and providing a Python environment to make the build results. This is such a perfect fit to Nuitka and a dependency that will likely remain.
The valgrind project
Luckily we can use Valgrind to determine if something is an actual improvement without the noise. And it's also helpful to determine what's actually happening when comparing.
Thanks for hosting the build infrastructure that the Debian and sponsor Yaroslav Halchenko uses to provide packages for all Ubuntu versions.
Thanks for hosting this excellent service that allows us to provide RPMs for a large variety of platforms and make them available immediately nearly at release time.
The MinGW64 project
Thanks for porting the gcc to Windows. This allowed portability of Nuitka with relatively little effort.
The Buildbot project
Thanks for creating an easy to deploy and use continuous integration framework that also runs on Windows and is written and configured in Python code. This allows running the Nuitka tests long before release time.
The isort project
Thanks for making nice import ordering so easy. This makes it so easy to let your IDE do it and clean up afterward.
The black project
Thanks for making a fast and reliable way for automatically formatting the Nuitka source code.
This document is written in REST. That is an ASCII format which is readable as ASCII, but used to generate PDF or HTML documents.
You will find the current source under: http://nuitka.net/gitweb/?p=Nuitka.git;a=blob_plain;f=README.rst
And the current PDF under: http://nuitka.net/doc/README.pdf