Matlab wrapper uses python 3

[mfinean]

Problem:
[ 56%] Generating wrap/gtsam/gtsam_wrapper.cpp
Ignoring classes: ['gtsam::Point2', 'gtsam::Point3']
Traceback (most recent call last):
File "/path/gtsam/wrap/matlab_wrapper.py", line 1770, in
cc_content = wrapper.wrap()
File "/path/gtsam/wrap/matlab_wrapper.py", line 1657, in wrap
self.wrap_namespace(self.module)
File "/path/gtsam/wrap/matlab_wrapper.py", line 1096, in wrap_namespace
self.wrap_namespace(element, namespaces)
File "/path/gtsam/wrap/matlab_wrapper.py", line 1101, in wrap_namespace
class_text = self.wrap_instantiated_class(element, "".join(namespace.full_namespaces()))
File "/path/gtsam/wrap/matlab_wrapper.py", line 1037, in wrap_instantiated_class
).splitlines()) + '\n'
File "/path/gtsam/wrap/matlab_wrapper.py", line 698, in wrap_class_constructors
methods_wrap = textwrap.indent(textwrap.dedent("""\

To generate the Matlab wrapper it requires python 3. I fixed by changing "Default" to my python 3 version.

gtsam/CMakeLists.txt

Line 104 in de75367

set(GTSAM_PYTHON_VERSION "Default" CACHE STRING "The version of Python to build the wrappers against.")

[ProfFan]

Ahh. Should be compatible with Python 2.7... #TODO

[varunagrawal]

I disagree that it should be compatible with Python 2.x.

Python 2 has officially reached EOL, so I recommend @mfinean upgrade his Python to 3.6+.

[varunagrawal]

Actually disregard my previous comment. This issue doesn't seem to have anything to do with Python 2.
@mfinean it seems that you haven't pasted the full stack trace and error message. Can you please do so?

[mfinean]

My apologies that it cut off! First error encountered was:

---

[ 56%] Generating wrap/gtsam/gtsam_wrapper.cpp
File "/home/mark/installs/gtsam/wrap/matlab_wrapper.py", line 87
print(message, file=sys.stderr)
^
SyntaxError: invalid syntax
gtsam/CMakeFiles/gtsam_matlab_wrapper.dir/build.make:76: recipe for target 'gtsam/wrap/gtsam/gtsam_wrapper.cpp' failed
make[2]: *** [gtsam/wrap/gtsam/gtsam_wrapper.cpp] Error 1
CMakeFiles/Makefile2:1188: recipe for target 'gtsam/CMakeFiles/gtsam_matlab_wrapper.dir/all' failed
make[1]: *** [gtsam/CMakeFiles/gtsam_matlab_wrapper.dir/all] Error 2
make[1]: *** Waiting for unfinished jobs....

---

This should have been my warning but I used
from __future__ import print_function
to bypass that. The next error was:

---

[ 58%] Building CXX object examples/CMakeFiles/Pose3SLAMExampleExpressions_BearingRangeWithTransform.dir/Pose3SLAMExampleExpressions_BearingRangeWithTransform.cpp.o
Ignoring classes: ['gtsam::Point2', 'gtsam::Point3']
Traceback (most recent call last):
File "/home/mark/installs/gtsam/wrap/matlab_wrapper.py", line 1769, in
cc_content = wrapper.wrap()
File "/home/mark/installs/gtsam/wrap/matlab_wrapper.py", line 1656, in wrap
self.wrap_namespace(self.module)
File "/home/mark/installs/gtsam/wrap/matlab_wrapper.py", line 1095, in wrap_namespace
self.wrap_namespace(element, namespaces)
File "/home/mark/installs/gtsam/wrap/matlab_wrapper.py", line 1100, in wrap_namespace
class_text = self.wrap_instantiated_class(element, "".join(namespace.full_namespaces()))
File "/home/mark/installs/gtsam/wrap/matlab_wrapper.py", line 1036, in wrap_instantiated_class
).splitlines()) + '\n'
File "/home/mark/installs/gtsam/wrap/matlab_wrapper.py", line 697, in wrap_class_constructors
methods_wrap = textwrap.indent(textwrap.dedent("""
AttributeError: 'module' object has no attribute 'indent'
gtsam/CMakeFiles/gtsam_matlab_wrapper.dir/build.make:76: recipe for target 'gtsam/wrap/gtsam/gtsam_wrapper.cpp' failed
make[2]: *** [gtsam/wrap/gtsam/gtsam_wrapper.cpp] Error 1
CMakeFiles/Makefile2:1188: recipe for target 'gtsam/CMakeFiles/gtsam_matlab_wrapper.dir/all' failed
make[1]: *** [gtsam/CMakeFiles/gtsam_matlab_wrapper.dir/all] Error 2
make[1]: *** Waiting for unfinished jobs....

---

I wasn't suggesting for it be made Python 2 compatible but rather that there could be a catch for this to ensure Python 3 is used. In my case, the default was still Python 2.

[varunagrawal]

Ah thanks a lot! So you're right, in that Default picks up Python 2 on your system (I am guessing you are using Ubuntu?). Setting the CMake variable GTSAM_PYTHON_VERSION (either via command line or ccmake) to 3.6 or whatever version of python you are using, should fix this issue as you have already discovered.

I guess the issue really is that we need to somehow enforce Python 3+ in the wrapper. @ProfFan

[varunagrawal]

@mfinean #526 uses CMake to find Python3 exclusively. This should solve this issue.

Can you checkout that PR and try it on your local machine to confirm?

[varunagrawal]

@mfinean PR #526 has been merged into develop. Can you please confirm it solves this issue for you?
If not, please feel free to reopen the issue.