Runtime Environment

The pyDevSup module initializes the interpreter during the registration phase of IOC startup with the pySetupReg registrar function.

#!../../bin/linux-x86_64/softIocPy2.7
# Interpreter not started
dbLoadDatabase("../../dbd/softIocPy.dbd",0,0)
softIocPy_registerRecordDeviceDriver(pdbbase)
# Interpreter started

An epicsAtExit cleanup handler is also registered at this time.

Several IOC Shell functions are also registered. py() executes a line of python code. pyfile() reads and interprets a python script.

py("import mymod;)
py("mymod.makeDev('one')")
py("mymod.makeDev('two')")

pyfile("myinit.py")

PYTHONPATH

The interpreter search path is automatically prefixed with the following additional paths:

• ${PWD}
• $(TOP)/python<PY_VER>/$(EPICS_ARCH)
• $(PYDEV_BASE)/python<PY_VER>/$(EPICS_ARCH)
• $(EPICS_BASE)/python<PY_VER>/$(EPICS_ARCH)

The environment variables EPICS_BASE, PYDEV_BASE, TOP, and EPICS_ARCH will be used if set. Compile time defaults are selected for EPICS_BASE, PYDEV_BASE, EPICS_ARCH. If TOP is not set then the this entry is omitted.

The default for PYDEV_BASE is the $(INSTALL_LOCATION) given when the pyDevSup module was built.

Build Environment

When building IOCs or installing files, include PYDEVSUP in your configure/RELEASE file.

PYDEVSUP=/dir/where/pyDevSup/is/installed
EPICS_BASE=/....

The default or preferred Python version can be specificed in configure/CONFIG_SITE

PY_VER ?= 2.7

The following should be added to individual EPICS Makefiles.

TOP=../..
include $(TOP)/configure/CONFIG
include $(PYDEVSUP)/configure/CONFIG_PY
...
include $(TOP)/configure/RULES
include $(PYDEVSUP)/configure/RULES_PY

This will add or amend several make variables. The USR_*FLAGS variables may be extended with appropriate flags for building python modules. The PY_VER variable is defined with the Python version number found in install directories (eg “2.7”). The PY_LD_VER variable is defined with the python library version number (eg “3.2mu”), which may be the same as PY_VER.

Include pyDevSup in your IOC

While the softIocPyX.Y executable(s) built as part of this module will be sufficient for many uses, it is also possible to include the pyDevSup modules in an IOC along with other drivers. This can be done in the usual way.

PROD_IOC = myioc
DBD += myioc.dbd
...
myioc_DBD += pyDevSup.dbd
...
myioc_LIBS += pyDevSup$(PY_LD_VER)

Installing .py files

Additional .py files can be installed as follows.

PY += mymod/__init__.py
PY += mymod/file1.py

Building extensions

For convenience, additional Python extensions can be build by the EPICS build system. In this example the extension name is “_myextname” and the resulting library is expected to provide the an initialization function named “init_myextname”.

LOADABLE_LIBRARY_HOST = _myextname

_myextname_SRCS += somefile.c

In somefile.c

PyMODINIT_FUNC init_myextname(void)

Installing for several Python versions

The recipe for building and installing the pyDevSup module for several python version side by side is

make PY_VER=2.6
make clean
make PY_VER=2.7
make clean
make PY_VER=3.2
make clean

The PYTHON make variable can be specified if the interpreter executable has a name other than python$(PY_VER).