Hi and thanks, I tried installing the newest Kwant version now, using: pip3 install git+https://gitlab.kwant-project.org/kwant/kwant.git@master but now I get a new error message (same code): File "/home/camilla/Kwant/Tests/conservation.py", line 91, in <module> main() File "/home/camilla/Kwant/Tests/conservation.py", line 68, in main syst = make_system(t=1.0, W=40, L=40, lead_W = 40) File "/home/camilla/Kwant/Tests/conservation.py", line 56, in make_system syst.attach_lead(lead) File "/home/camilla/.local/lib/python3.5/site-packages/kwant/builder.py", line 1402, in attach_lead self.leads.append(BuilderLead(lead_builder, tuple(interface))) File "/home/camilla/.local/lib/python3.5/site-packages/kwant/builder.py", line 566, in __init__ self.interface = tuple(sorted(interface)) TypeError: unorderable types: tinyarray.ndarray_int() < tinyarray.ndarray_int() [Finished in 1.4s with exit code 1] should I have installed differently. According to pip3 I have installed kwant (1.3.0a0.dev123+g3961899) Sincerely, Camilla