cysgp4 has the following strict requirements:

Installing cysgp4

Using Anaconda

The easiest way to install cysgp4 is certainly to make use of the great Anaconda Python distribution:

conda install cysgp4 -c conda-forge

Using pip

To install cysgp4 with pip, simply run

pip install cysgp4


You may need a C++ compiler (e.g., g++) with OpenMP support to be installed for the installation to succeed, if no binary wheel is available for your OS and Python version on the Python Package Index


Use the --no-deps flag if you already have dependency packages installed, since otherwise pip will sometimes try to “help” you by upgrading your installation, which may not always be desired.


If you get a PermissionError this means that you do not have the required administrative access to install new packages to your Python installation. In this case you may consider using the --user option to install the package into your home directory. You can read more about how to do this in the pip documentation.

We recommend to use a Python distribution, such as Anaconda, especially, if you are on Installation on Windows.

Do not install cysgp4 or other third-party packages using sudo unless you are fully aware of the risks.

Installation from source

There are two options, if you want to build cysgp4 from sources. Either, you install the tar-ball (*.tar.gz file) from PyPI and extract it to the directory of your choice, or, if you always want to stay up-to-date, clone the git repository:

git clone

Then go into the cysgp4 source directory and run:

pip install .

Again, consider the --user option or even better use virtualenv or a Python distribution such as Anaconda to avoid messing up the system-wide Python installation.

Installation on Windows

Note that for Windows machines we provide a binary wheel (Python 3.5+ only) via PyPI and installation is as easy as with Linux:

pip install cysgp4


If you are desperate, you can install cysgp4 from source even on Windows. You’ll need to install a suitable C++-compiler; see here. The cysgp4 package needs Python 3.5 or later, which means VC++ Version 14 is mandatory. The easiest way to obtain it, is by installing the Visual C++ 2015 Build Tools which is “only” 4 GBytes large…

Installation on MacOS

Installation on MacOS can be a bit tricky, because the standard C++ compiler does not support OpenMP. We provide wheels on PyPI, such that you can

pip install cysgp4

however, you need to have the GCC C++ compiler (see below), otherwise you’ll likely get some error message.

Also, if you want to install from source, you must have a C++ compiler. There are basically two options, using the gcc suite (recommended) or clang/LLVM.


brew install gcc
brew link --overwrite gcc

You may have to set build-related environment variables to point towards the gcc compilers instead of the standard clang:

export CC="gcc-8"
export CXX="g++-8"
export CPP="g++-8"
export LD="gcc-8"
export LDFLAGS="-Wl,-rpath,/usr/local/opt/gcc/lib/gcc/8/"


Replace the version (“8”) in the above lines with the actually installed gcc version!

Then follow the instructions in Installation from source.


brew update
brew install llvm

export CC='/usr/local/opt/llvm/bin/clang'
export CXX='/usr/local/opt/llvm/bin/clang++'
export CXX11='/usr/local/opt/llvm/bin/clang++'
export LDFLAGS='-L/usr/local/opt/llvm/lib -Wl,-rpath,/usr/local/opt/llvm/lib -lgomp'
export CPPFLAGS='-I/usr/local/opt/llvm/include -stdlib=libc++'

Then follow the instructions in Installation from source.


The MacOS wheel, which we provide on PyPI (for pip installation) was built using clang/LLVM. So it may happen that you run into binary incompatibilities if you use a different compiler suite on your computer. In such cases it may be necessary to build cysgp4 from source using your own compiler. Sometimes even different compiler versions (e.g. gcc 6.3 instead of gcc 6.4) can lead to problems. Please write a ticket, if you run into trouble.


Again, if you’re on Anaconda, things get (often) much simpler:

conda install -c conda-forge gcc

This will install the gcc compiler suite into your Anaconda installation and the instructions in Installation from source should work out-of-the-box. If you prefer clang/LLVM, the following should install the necessary conda packages:

conda install -c conda-forge clang_osx-64 clangxx_osx-64 llvm-openmp openmp

The cysgp4 package on conda-forge was created using the latter approach.

Testing an installed cysgp4

The easiest way to test if your installed version of cysgp4 is running:

pytest --pyargs cysgp4.tests


This way of running the tests may not work if you do it in the cysgp4 source distribution directory.

It is also possible to use the test() function:

import cysgp4

but currently, this will only work, if the user has Astropy installed (this may change soon). The tests should run and print out any failures, which you could report at the cysgp4 issue tracker.

If you prefer testing on the command line and want to develop in the source code, you can also utilize tox and run the following in the source directory:

tox -e test