@spiceErrorCheck<EOL>def halfpi():
return libspice.halfpi_c()<EOL>
Return half the value of pi (the ratio of the circumference of
a circle to its diameter).

http://naif.jpl.nasa.gov/pub/naif/toolkit_docs/C/cspice/halfpi_c.html

:return: Half the value of pi.
:rtype: float