(side note) On archlinux that also uses system Python for Sage the situation is better: importing sage.all in Python2 does work! Even though the configuration constants are not in the environment! They are set up properly in sage_env.py that is part of the SageMath installation. And more precisely $SAGE_LOCAL fallsback to the default "/usr" which is what it is intend to be on archlinux.
I don't understand why on Debian $SAGE_LOCAL is set to None and managed by environment variables. Le 10/01/2019 à 04:47, Nathan Dunfield a écrit :
I am a developer of the Python package "snappy" which acquires extra features when imported inside of Sage. Some of our Linux users have recently reported difficulties with SnapPy on machines where Sage was installed by the standard package manger making use of the system libraries and in particular the system python. I have reproduced the problem on Debian Sid but it also manifests itself on Fedora 28 [1]. The root of our problem is that in this situation: python -c "import sage.all" results the error: Traceback (most recent call last): File "<string>", line 1, in <module> File "/usr/lib/python2.7/dist-packages/sage/all.py", line 71, in <module> from sage.env import SAGE_ROOT, SAGE_SRC, SAGE_DOC_SRC, SAGE_LOCAL, DOT_SAGE, SAGE_ENV File "/usr/lib/python2.7/dist-packages/sage/env.py", line 123, in <module> _add_variable_or_fallback('SAGE_ETC', opj('$SAGE_LOCAL', 'etc')) File "/usr/lib/python2.7/dist-packages/sage/env.py", line 103, in _add_variable_or_fallback value = sep.join(components) TypeError: sequence item 0: expected string, NoneType found whereas sage -python -c "import sage.all" works as expected. Currently, our Python package tests for whether it is running in SageMath by: _within_sage = False try: import sage.all _within_sage = True except ImportError: pass One solution for us (I think) would be to simply catch and ignore all types of exceptions in the above block, but I was wondering if the current behavior of 'python -c "import sage.all"' was expected or is this possibly a bug? Or perhaps there is a work-around of some kind? Thanks, Nathan P.S. In the Debian package "sage" does not accept the "-pip" flag, even though installing the "sagemath" package does pull in "pip" (tested on a clear Sid Docker container). Why is this? I ask because our current instructions for installing SnapPy into SageMath use "sage -pip". [1] See the second comment, not the original report, on https://bitbucket.org/t3m/snappy/issues/14/
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