Re: [ESPResSo-users] attribution errors on swimming feature

[Henri]

Dear Le,

I'm very sorry but I can't reproduce your issue with the latest python branch.  
Here I show the
steps I took to get the example working on my machine

git clone https://github.com/espressomd/espresso.gitcd espresso
mkdir build
cd build
cmake ..
cp myconfig-sample.hpp myconfig.hpp
# Uncomment features from your mailing in myconfig.hpp
cmake ..
make

Then I run the tutorial script using

./pypresso 
../doc/tutorials/python/06-active_matter/SOLUTIONS/enhanced_diffusion.py 1.0

and it works for me without errors.

At the same time it seems like you are using a different version of ESPResSo to 
run the interactive
example and the tutorial code, because the interactive example does not show 
any errors
(The <espressomd.particle_data.ParticleHandle ...> bit is only a representation 
of the return value
of system.part.add).

Kind regards,
Henri

On Wed, 2017-10-25 at 17:15 -0400, Le Qiao wrote:
> Hi,
> 
> I’m trying add a self propelling particle with the swimming feature on by 
> using the code example:
> 
>             Examples
>             --------
>             >>> import espressomd
>             >>> 
>             >>> system = espressomd.System()
>             >>> 
>             >>> # Usage with Langevin
>             >>> system.part.add(id=0, pos=[1,0,0],swimming={'f_swim':0.03})
>             >>> 
>             >>> # Usage with LB
>             >>> system.part.add(id=1, pos=[2,0,0],swimming={
>             >>>    'f_swim':0.01, 'mode':'pusher', 'dipole_length':2.0, 
> 'rotational_friction':20})
> 
> However, it kept giving me errors:
> 
> $ ./pypresso 
> Python 2.7.14 (default, Sep 25 2017, 09:54:19) 
> [GCC 4.2.1 Compatible Apple LLVM 9.0.0 (clang-900.0.37)] on darwin
> Type "help", "copyright", "credits" or "license" for more information.
> >>> import espressomd
> >>> system = espressomd.System()
> >>> system.part.add(id=0, pos=[1,0,0],swimming={'f_swim':0.03})
> <espressomd.particle_data.ParticleHandle object at 0x10947a8a0>
> >>> 
> >>> system.part.add(id=1, pos=[2,0,0],swimming={'f_swim':0.01, 
> >>> 'mode':'pusher',
> 'dipole_length':2.0, 'rotational_friction':20})
> <espressomd.particle_data.ParticleHandle object at 0x10947aee0>
> >>> exit()
> 
> 
> 
> 
> I also tried the example code from tutorial directory:  
> doc/tutorials/python/06-
> active_matter/SOLUTIONS/enhanced_diffusion.py
> 
> 
> I got following error:
> Traceback (most recent call last):
>   File "enhanced_diffusion.py", line 87, in <module>
>     system.part.add(pos=[5.0, 5.0, 5.0],swimming={ 'v_swim' : vel 
> },rotation=[1,1,1])
>   File "espressomd/particle_data.pyx", line 1744, in 
> espressomd.particle_data.ParticleList.add
> (/home/mbcx/project/Work/test/espresso/build/src/python/espressomd/particle_data.cpp:14337)
>   File "espressomd/particle_data.pyx", line 1772, in
> espressomd.particle_data.ParticleList._place_new_particle
> (/home/mbcx/project/Work/test/espresso/build/src/python/espressomd/particle_data.cpp:14674)
>   File "espressomd/particle_data.pyx", line 1476, in
> espressomd.particle_data.ParticleHandle.update
> (/home/mbcx/project/Work/test/espresso/build/src/python/espressomd/particle_data.cpp:10383)
> AttributeError: 'espressomd.particle_data.ParticleHandle' object has no 
> attribute 'swimming'
> 
> But I did enable the engine feature, Does anyone know what is the cause of 
> the errors? 
> 
> 
> Enabled features in myconfig.hpp
>   #define CONSTRAINTS
>   #define MASS
>   #define ENGINE
>   #define ROTATION
>   #define ROTATIONAL_INERTIA
>   #define LB
>   #define LB_BOUNDARIES
>   #define LENNARD_JONES
> 
> Cheers
> Le