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hou from a Regular Python Shell
By simply importing the
hou module into a regular Python shell, you can
easily integrate Houdini into your existing Python-based scripts. The first
time you import
hou, Python will load in all of Houdini’s libraries and
initialize an empty Houdini session. The
hou module effectively stores a
Houdini session, and you can load into that session from a hip file, inspect
that file from your script, and input and output information to and from nodes
in that session.
In order to import the
hou module, you need to tell Python to search in
$HFS/houdini/python2.7libs for Python modules. One way to accomplish this
is to append this to the PYTHONPATH environment variable before starting
Python, and another is to append the path to the
sys.path from within Python.
The following Python snippet will import the
hou module into a standard
Python shell, assuming that you sourced
houdini_setup to set
If you do not run
source houdini_setup, you must set the HFS environment
variable manually. Also, on Windows, you must append the value of $HFS/bin
to the PATH environment variable.
When you import the
hou module, the standard Houdini initialization scripts
123.cmd/123.py and 456.cmd/456.py will run.
#!/usr/bin/python def enableHouModule(): '''Set up the environment so that "import hou" works.''' import sys, os # Importing hou will load in Houdini's libraries and initialize Houdini. # In turn, Houdini will load any HDK extensions written in C++. These # extensions need to link against Houdini's libraries, so we need to # make sure that the symbols from Houdini's libraries are visible to # other libraries that Houdini loads. So, we adjust Python's dlopen # flags before importing hou. if hasattr(sys, "setdlopenflags"): old_dlopen_flags = sys.getdlopenflags() import DLFCN sys.setdlopenflags(old_dlopen_flags | DLFCN.RTLD_GLOBAL) try: import hou except ImportError: # Add $HFS/houdini/python2.7libs to sys.path so Python can find the # hou module. sys.path.append(os.environ['HFS'] + "/houdini/python%d.%dlibs" % sys.version_info[:2]) import hou finally: if hasattr(sys, "setdlopenflags"): sys.setdlopenflags(old_dlopen_flags) enableHouModule() import hou
When you import the
hou module, Python will check out a license. By
default, it will use a Houdini Batch license, and use a Houdini FX
license if no batch license could be found. If you want it to use a
Houdini license, you can set the HOUDINI_SCRIPT_LICENSE variable
hescape before importing the hou module. You can also set this
variable from within your Python script with
os.environ['HOUDINI_SCRIPT_LICENSE'] = 'hescape'.
By default, the
hou module will not return the Houdini license until the
Python interpreter exits. However, if you have a long running Python
script and want to quickly acquire and release a license, you can call
hou.releaseLicense() when you are done with the
hou module. Subsequent
calls into the
hou module will reacquire the license. Note that Houdini’s
session data and libraries will not be unloaded from memory until Python exits.
hou module, when imported by Python or Houdini, will loop through the
directories in $HOUDINI_PATH, and for each directory found, append that
directory plus "/python2.7libs" to sys.path. For backward compatibility with
older versions of Houdini, it will also look for the directories in
$HOUDINI_PATH plus "/scripts/python". For example, you can put your Python
modules in the directory
$HOME/houdiniX.Y/python2.7libs and they will be
in the Python search path after you import
Hython is a Python shell that ships with Houdini that is slightly different from the standard Python shell in the following ways:
It automatically adds
$HFS/houdini/python2.7libsto sys.path and imports the hou module when it starts up.
You can pass .hip files on the command line and it will load them.
It supports tab completion, and you can press tab twice to list possible completions (on Linux and Mac).
You can run hscript commands from an interactive shell by prefixing them with
It can receive and handle Houdini openport commands while waiting for console input when you start it with the
By default, hython does not listen in the background for and run commands sent
to openport sockets, but you can enable this behavior with the
option. When listening for openport events, hython uses a different mechanism
to read command-line input than the standard Python one. Note that this
other mechanism may leave the console in a bad state if hython forks into the
background or exits prematurely, and it can behave strangely when editing lines