MacOS Installation

Unless otherwise noted, the commands in these instructions are run from the MacOS terminal (command line).

Installation requires a working Python environment and compilers. The two common ways to achieve this are via conda or via MacPorts. As a weak recommendation for choosing between them, conda may be better if your main focus is running Python and you need conda’s easy support for multiple Python environments; MacPorts may be better if you want to use many of the other open source tools provided in MacPorts.

Binary installers for SpacePy on Mac are in preparation for a future release.

Conda installation

Our recommendation for Anaconda is to use Python 3 and 64-bit binaries. Follow the directions to install conda and set up an environment; a minimal setup can be had by downloading the latest miniconda. Double-click the miniconda pkg and run through the installation process, choosing “install for me only”. Then, at the terminal:

source ~/opt/miniconda3/bin/activate

You will now be in an active conda environment. (Note: the installation will modify your .zprofile file.)

Compiling under conda requires the MacOS 10.9 SDK on Intel (x86_64) Macs and 11.0 on Apple Silicon (ARM/M1/M2). It can be downloaded here (choose “MacOSX10.9.sdk.tar.xz” or “MacOSX11.0.sdk.tar.xz”). Uncompress it into opt, e.g.:

sudo tar xf ~/Downloads/MacOSX10.9.sdk.tar.xz -C /opt

Install the Fortran compiler:

conda install gfortran

If you do not have Xcode installed, you will be prompted with a message like “The xcrun command requires the command line developer tools.” Accept the installation and allow it to finish before continuing.

You may optionally install SpacePy dependencies via conda (otherwise they will be installed via pip):

conda install numpy scipy matplotlib h5py

Finally, install SpacePy:

SDKROOT=/opt/MacOSX10.9.sdk pip install spacepy  # Intel
SDKROOT=/opt/MacOSX11.0.sdk pip install spacepy  # ARM

If you’re installing as a single user (not in a virtual environment) then add the --user flag.

You will also need the NASA CDF library to use pycdf.

MacPorts installation

You may install the full Xcode suite and follow the MacPorts guide; however, these directions should suffice to install a working Python and SpacePy.

Installing the Xcode command line tools is recommended before proceeding:

xcode-select --install

Download the MacPorts installer and double-click the pkg to perform the installation. (Note this modifies your .zprofile environment file.)

Install Python and the needed compilers. You need to specify a version; at this time, Python 3.9 and gcc 11 are reasonable choices:

sudo port install gcc11  # Includes gfortran
sudo port install python39
sudo port install py39-pip
# Installing the following is optional; pip will automatically install
sudo port install py39-numpy py39-scipy py39-h5py py39-matplotlib

If you have not already installed the Xcode command line tools, you will be prompted to do so. In that case, it is suggested to accept the tools installation, and then quit the port command and restart once the tools are installed.

To install via pip, default versions of Python and gcc must be set:

sudo port select --set python python39
rehash #recalculate the pathing to not get system python
sudo port select --set python3 python39
sudo port select --set pip pip39
sudo port select --set gcc mp-gcc11

Then you can install SpacePy:

pip install spacepy

If you’re installing as a single user (not in a virtual environment) then add the --user flag.

You will also need the NASA CDF library to use pycdf.

If you are installing from a source distribution, you can specify the compiler at install time instead of using port select:

python3.9 install --fcompiler=gnu95 --f90exec=/opt/local/bin/gfortran-mp-11


NASA provides Mac binaries of the CDF library. Download the file ending in binary_signed.pkg (e.g. CDF3_8_1-binary_signed.pkg), double-click, and install per the defaults.

Xcode installation

Installation of the full Xcode package is not required simply for SpacePy; however, if you are interested in regular compiler use, it may be useful. If you choose to install the full Xcode package, perform these steps before installing conda or macports via the directions above.

  • Create and log in to an Apple developer account at

  • Check the Xcode release notes to find the latest version of Xcode supported on your version of MacOS.

  • From the more downloads section of the Apple Developer site, search for and download that version of Xcode.

  • Double-click on the downloaded .xip file to open with the archive utility and extract the Xcode app.

  • Drag the resulting Xcode icon into Applications

  • From the more downloads section of the Apple Developer site, search for the Xcode command line tools for the same version of Xcode

  • Open the dmg file with the command line tools, open the resulting mounted disk image, and double-click the pkg file to install.

Proceed with the installation of conda or MacPorts and SpacePy