The following instructions will install flatlib from the source files. In the future, binaries may be made available and the instructions will be updated accordingly.


If you don’t have Python 3 installed on your system, download and install the latest Python 3.4 for Windows from You can check if the interpreter was correctly installed by executing py on the command line.

Open a Windows command prompt (or exit the Python interactive shell) and install flatlib using py -m pip install flatlib.

If you get an error such as Microsoft Visual C++ 10.0 is required (Unable to find vcvarsall.bat), you will have to install a C compiler. The compiler is required to build pyswisseph - the Python port of the Swiss Ephemeris.

There are several C compilers for Windows, such as Cygwin and MinGW, but Visual C++ 2010 is the most used for compiling Python 3 extensions on Windows. Download Microsoft Visual C++ 2010 Express from (it may require the creation of a free Windows Developer account). After the installation, execute the following on the command line:

set CL=-DWIN32
py -m pip install flatlib

You should now have flatlib installed in your system.


Latest versions of OS X are bundled only with Python 2. The preferred way to install Python 3 in OS X is using the homebrew package manager ( Install homebrew and then install Python 3 using brew install python3.

Before you install flatlib, you must have a C compiler in your system. This is because flatlib depends on the Swiss Ephemeris which is implemented in C. Fortunatelly, Apple provides the Xcode Command Line Tools which bundles a C compiler. To install it, open the terminal (Applications/Utilities/Terminal) and execute gcc. You’ll see an alert box if you don’t have a compiler installed:


If you don’t need the entire Xcode (about 2.5GB) just press Install..

Finally, to install flatlib use pip3 install flatlib.


Python 3 is already included on most of the newer distributions. The simplest way to test for the existence of Python 3 is to open the terminal and execute python3 to start the interactive python interpreter. If the interpreter is not found, you will have to install it from your distribution’s repo.

To install flatlib, use pip3 install flatlib. It may require you to install pip and other python 3 development libraries.

If you get a Permission Denied error, execute the previous command with sudo.

Testing the installation

Start the python3 interactive interpreter (python3 on Linux and Mac, and py on Windows) and execute the following:

>>> import flatlib
>>> flatlib
<module 'flatlib' from '/usr/local/lib/python3.4/dist-packages/flatlib/'>

If you don’t get an import error, flatlib is installed in your system.

Upgrading from a previous version

To upgrade from a previous version, run:

  • pip3 install flatlib --upgrade in Linux and Mac.
  • py pip install flatlib --upgrade in Windows.


Just do pip3 uninstall flatlib on Linux and Mac or py pip uninstall flatlib on Windows.