The old Numeric-Python based ASE-2 can coexist with the new numpy-based ASE-3, because the two packages have different names: ASE and ase respectively. Here is an example of combining both:
from ASE.Trajectories.NetCDFTrajectory import NetCDFTrajectory
traj = NetCDFTrajectory('a.nc')
loa = traj.GetListOfAtoms(-1)
# Convert to new style Atoms object:
from ase import *
a = Atoms(loa)
The new ASE can actually read old NetCDF trajectory files, so this would be simpler:
from ase import *
a = read('a.nc')
Note
Reading old NetCDF files in the new ASE, works even without having the libnetcdf and Scientific.IO.NetCDF libraries installed.
Use the ASE2ase tool (source code tools/ASE2ase) to convert old scripts:
$ ASE2ase oldscript.py
$ diff -u oldscript.py.bak oldscript.py
Check that the differences look OK. The conversion tool isn’t clever enough to get everything right, so you will have to do some conversion manually also. If you have any problems doing this, then you should not hesitate to contact the campos-devel mailing list (see Mailing Lists) and ask for help.