Basics of SpiceyPy¶
Follow the installation instructions provided in installation.
Confirm SpiceyPy installation¶
There are multiple ways to verify your SpiceyPy installation. The first test is to simply run
You should see SpiceyPy in the list of your installed packages. If SpiceyPy is not present in the list then a configuration issue in your environment caused SpiceyPy to be installed in a non-standard way. Note this is an error prone to systems with multiple installed python versions.
If SpiceyPy is present in the pip list, then SpiceyPy is installed. Another verification step is within the python REPL run:
import spiceypy as spice
The version of the installed cspice toolkit (note: not SpiceyPy’s version) should be printed out. Otherwise the Python interpreter should output an explanitory error message.
A simple example program¶
The following calls the SPICE function
spiceypy.spiceypy.tkvrsn() which outputs the version
of cspice that SpiceyPy is wrapping.
import spiceypy as spice spice.tkvrsn('TOOLKIT')
This should output the following string:
SpiceyPy by default checks the spice error system for errors after all function calls and will raise SpiceyErrors (a python exception) when spice indicates an error. The exception message is a string that follows the format used elsewhere in spice and includes the toolkit version, the short description, explanation, long format description, and traceback (of spice calls). Read the NAIF tutorial on exceptions here.
Also, by default SpiceyPy captures the ‘found’ flags some functions return as it is not
idiomatic to python and instead through a SpiceyError exception. This can be temporarily disabled using
spiceypy.spiceypy.no_found_check() context manager that allows the found
flag to be returned to the user for action. Outside the context SpiceyPy functions will revert to default behavior.
import spiceypy as spice spice.bodc2n(-9991) # will raise an exception with spice.no_found_check(): name, found = spice.bodc2n(-9991) # found is now available, no exception raised! assert not found # found is going to be False in this case. spice.bodc2n(-9991) # will raise an exception again
There is also an accompanying context manager for enabling the default spiceypy behavior within a code block like so:
import spiceypy as spice spice.bodc2n(-9991) # will raise an exception with spice.found_check(): name = spice.bodc2n(-9991) # will also raise an exception
In addition, for advanced users there are two function
which will disable and enable the behavior without use of the context manager. Additionally, a method
spiceypy.spiceypy.get_found_catch_state() allows users
to query the current state of found flag catching setting.