Adding __init__.py fixes the problem but then I've to use `from z3.z3 import *` rather than `from z3 import *`. The proper fix would be, as noted by OP, install the z3*.py at top level.
Interestingly, in lp v4.4.0-2 of the package, the changelog (https://launchpad.net/ubuntu/+source/z3/4.4.0-2) mentions adding __init__.py but it isn't included in the amd64 .deb.
Adding __init__.py fixes the problem but then I've to use `from z3.z3 import *` rather than `from z3 import *`. The proper fix would be, as noted by OP, install the z3*.py at top level.
Interestingly, in lp v4.4.0-2 of the package, the changelog (https:/ /launchpad. net/ubuntu/ +source/ z3/4.4. 0-2) mentions adding __init__.py but it isn't included in the amd64 .deb.