How to depend on sagemath as pip installable third party package

[Maarten Derickx]

Hi,

I maintain a pip installable python package that depends on sagemath. And installing this package in sage using

sage -pip install git+https://github.com/koffie/mdsage.git

recently broke. When I looked at why it broke I was happily surprised because it seems that sagemath is now finally uploading packages to pypi. The reason this breaks is because I was relying on the behavior of the old "fake" sagemath pypi package that essentially was just a package that only checked if the sage library was available in that python environment.

But now it seems that sagemath really is finally starting to behave like a proper python library.

My question is, going forward what will be the recommended way to depend on sagemath in a pip package, and how to tell end users to install my pip package in an already working sage installation?

At the moment I fixed the problems by pinning the sagemath python package version to 1.3.0 . But I am sure that this is not the proper way forward.

See below for what goes wrong in sagemath 10.3 and 10.5

~$ sage -pip install git+https://github.com/koffie/mdsage.git@devel
Defaulting to user installation because normal site-packages is not writeable
Collecting git+https://github.com/koffie/mdsage.git@devel
  Cloning https://github.com/koffie/mdsage.git (to revision devel) to /tmp/pip-req-build-h6_c3fau
  Running command git clone --filter=blob:none --quiet https://github.com/koffie/mdsage.git /tmp/pip-req-build-h6_c3fau
  Running command git checkout -b devel --track origin/devel
  Switched to a new branch 'devel'
  Branch 'devel' set up to track remote branch 'devel' from 'origin'.
  Resolved https://github.com/koffie/mdsage.git to commit ebe7afdf1fcfec8d8737a7a51a02b2a638aa2f74
  Preparing metadata (setup.py) ... done
Collecting sagemath>=10.7.0 (from mdsage==0.1.0)
  Using cached sagemath-10.7.tar.gz (30.9 MB)
  Installing build dependencies ...


The log goes on for quite a bit. But as you can imagine it should already be clear at this point that it will fail, since installing sage 10.7 in the python environment of an older sage version doesn't sound like a good idea.

Thanks,
Maarten

[Tobia...@gmx.de]

Thanks for bringing this up!

>  what will be the recommended way to depend on sagemath in a pip package

As with any other python dependency: If you compile against sage (eg using cython), you should specify `sagemath` under `build-system > requires` in the pyproject.toml of your project. If sage is just a runtime dependency, then put it under `project > dependencies`.

>  how to tell end users to install my pip package in an already working sage installation

Ideally, it would be like any other pip package: tell users to activate the venv they want to install it in, then run `pip install <your pip package>`. However, if you have sagemath declared as build requirement, then this might build sage again (if there is no cached wheel) since pip creates a new empty build env by default. To prevent that, one should use `pip install --no-build-isolation <your pip package>` in the sage venv.

We should add some documentation for downstream sagemath packages.

[Dima Pasechnik]

Hi Maarten,
IMHO you'd need to update your package to work with modern setuptools
(no distutils).
Just think of sage as of a Python dependency. (It still works, in
fact, but this might not be
for too long).

If one has Sage installed and running in a "usual" venv, then
installing your package breaks it, because it uninstalls sagemath and
"installs" meaningless sagemath 1.3.0.

(sage-src) dima@tarski ~/software/sage-src $ ./sage # all works...
┌────────────────────────────────────────────────────────────────────┐
│ SageMath version 10.8.beta2, Release Date: 2025-09-07 │
│ Using Python 3.13.5. Type "help()" for help. │
└────────────────────────────────────────────────────────────────────┘
┏━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┓
┃ Warning: this is a prerelease version, and it may be unstable. ┃
┗━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┛
sage:
(sage-src) dima@tarski ~/software/sage-src $ cd tmp
(sage-src) dima@tarski ~/software/sage-src/tmp $ git clone
g...@github.com:koffie/mdsage.git
Cloning into 'mdsage'...
[...]
(sage-src) dima@tarski ~/software/sage-src/tmp $ cd mdsage
(sage-src) dima@tarski ~/software/sage-src/tmp/mdsage $ uv pip install .
Using Python 3.13.5 environment at: /home/dima/software/sage-src/.venv
Resolved 3 packages in 484ms
Built mdsage @ file:///home/dima/software/sage-src/tmp/mdsage
Prepared 1 package in 159ms
Uninstalled 1 package in 37ms
Installed 2 packages in 9ms
+ mdsage==0.1.0 (from file:///home/dima/software/sage-src/tmp/mdsage)
- sagemath==10.8b2 (from file:///home/dima/software/sage-src)
+ sagemath==1.3.0
(sage-src) dima@tarski ~/software/sage-src/tmp/mdsage $ ./sage
bash: ./sage: No such file or directory
(sage-src) dima@tarski ~/software/sage-src/tmp/mdsage $ cd ../../
(sage-src) dima@tarski ~/software/sage-src $ ./sage # oops :-(
Traceback (most recent call last):
File "/home/dima/software/sage-src/src/bin/sage-ipython", line 9, in <module>
from sage.misc.banner import banner
ModuleNotFoundError: No module named 'sage'


However, if I do the same, but with your requirements.txt removed, then
the above sequence just works.

Moreover, tests pass (one fails due to a deprecation notice)

$ ./sage -t tmp/mdsage/mdsage
Running doctests with ID 2025-09-07-21-50-34-567e0d32.
Git branch: HEAD
Git ref: 10.8.beta0-715-g31babe2a65d-dirty
Running with SAGE_LOCAL='/home/dima/software/sage-src/local' and
SAGE_VENV='/home/dima/software/sage-src/local/var/lib/sage/venv-python3.13'
Using --optional=gentoo,pip,sage
Features to be detected:
4ti2,SAGE_SRC,benzene,bliss,buckygen,conway_polynomials,coxeter3,csdp,cvxopt,cvxopt,database_cremona_ellcurve,database_cremona_mini_ellcurve,database_cubic_hecke,database_ellcurves,database_graphs,database_jones_numfield,database_knotinfo,dot2tex,dvipng,ecm,flatter,fpylll,fricas,gap_package_atlasrep,gap_package_design,gap_package_grape,gap_package_guava,gap_package_hap,gap_package_polenta,gap_package_polycyclic,gap_package_qpa,gap_package_quagroup,gfan,giac,glucose,graphviz,imagemagick,info,ipython,jmol,jupymake,jupyter_sphinx,kenzo,khoca,kissat,latte_int,lrcalc_python,lrslib,mathics,matroid_database,mcqd,meataxe,meson_editable,mpmath,msolve,nauty,networkx,numpy,palp,pandoc,pdf2svg,pdftocairo,pexpect,phitigra,pillow,plantri,polytopes_db,polytopes_db_4d,pplpy,primecountpy,ptyprocess,pycosat,pycryptosat,pynormaliz,pyparsing,python_igraph,regina,requests,rpy2,rubiks,sage.combinat,sage.geometry.polyhedron,sage.graphs,sage.groups,sage.libs.braiding,sage.libs.ecl,sage.libs.flint,sage.libs.gap,sage.libs.giac,sage.libs.homfly,sage.libs.linbox,sage.libs.m4ri,sage.libs.ntl,sage.libs.pari,sage.libs.singular,sage.misc.cython,sage.modular,sage.modules,sage.numerical.mip,sage.plot,sage.rings.complex_double,sage.rings.finite_rings,sage.rings.function_field,sage.rings.number_field,sage.rings.padics,sage.rings.polynomial.pbori,sage.rings.real_double,sage.rings.real_mpfr,sage.sat,sage.schemes,sage.symbolic,sage_numerical_backends_coin,sagemath_doc_html,scipy,singular,sirocco,sloane_database,sphinx,symengine_py,sympy,tdlib,threejs,topcom
Doctesting 14 files.
sage-runtests --warn-long 5.0
--random-seed=177091587185286457373292283220227525984
tmp/mdsage/mdsage/__init__.py
[0 tests, 0.00s wall]
sage-runtests --warn-long 5.0
--random-seed=177091587185286457373292283220227525984
tmp/mdsage/mdsage/canonical_rings.py
[14 tests, 0.40s wall]
sage-runtests --warn-long 5.0
--random-seed=177091587185286457373292283220227525984
tmp/mdsage/mdsage/congruence_subgroups.py
[6 tests, 1.14s wall]
sage-runtests --warn-long 5.0
--random-seed=177091587185286457373292283220227525984
tmp/mdsage/mdsage/cuspidal_classgroup.py
[17 tests, 1.54s wall]
sage-runtests --warn-long 5.0
--random-seed=177091587185286457373292283220227525984
tmp/mdsage/mdsage/kamiennys_criterion.py
**********************************************************************
File "tmp/mdsage/mdsage/kamiennys_criterion.py", line 1079, in
mdsage.kamiennys_criterion.KamiennyCriterion.?
Failed example:
C.verify_criterion(4)
Expected:
(True,
'All conditions are satified for Gamma1 d=4 p=43. Using n=5,
modp=65521, q=3 in Kamienny Version 1.5 and SageMath version ...',
[Vector space of degree 4 and dimension 0 over Finite Field of size 2
Basis matrix:
[], Vector space of degree 23 and dimension 2 over Finite Field of size 2
Basis matrix:
[1 1 0 1 0 0 1 1 1 0 1 0 1 1 1 1 1 1 0 0 1 0 0]
[0 0 1 0 1 1 1 0 1 1 0 1 1 1 1 0 1 1 1 1 0 0 0], Vector space of
degree 42 and dimension 11 over Finite Field of size 2
Basis matrix:
[1 0 0 0 0 0 0 1 0 1 1 1 0 1 1 0 1 0 1 0 1 0 0 0 0 0 1 0 1 0 0 0
1 1 0 0 1 1 1 1 1 1]
[0 1 0 0 0 0 0 0 0 1 0 1 0 1 0 1 1 0 0 0 0 0 1 0 1 1 0 0 1 0 0 0
1 1 1 1 0 0 0 1 0 0]
[0 0 1 0 0 0 0 0 0 1 0 0 0 0 0 1 1 1 0 0 1 0 0 0 0 0 0 0 0 1 1 1
0 0 0 0 1 1 0 0 1 0]
[0 0 0 1 0 0 0 0 0 1 0 0 0 0 1 1 1 0 1 0 0 0 0 0 1 1 0 0 1 0 0 0
0 1 0 1 0 0 0 1 0 0]
[0 0 0 0 1 0 0 1 0 1 0 0 1 0 0 1 1 0 0 0 0 0 0 0 0 1 0 0 1 0 0 0
0 1 0 0 0 0 0 0 0 0]
[0 0 0 0 0 1 0 1 0 0 0 1 1 0 0 1 1 1 1 1 1 0 1 0 0 1 1 0 0 1 1 1
0 0 1 0 0 0 1 1 0 1]
[0 0 0 0 0 0 1 0 0 0 1 0 1 1 1 0 1 1 0 1 0 0 1 0 0 0 1 0 1 0 1 0
0 1 1 0 0 0 1 1 1 1]
[0 0 0 0 0 0 0 0 1 1 1 0 0 0 0 1 1 0 0 1 0 0 0 0 0 0 0 0 0 0 1 0
0 0 0 0 1 1 0 0 0 0]
[0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 0 1 0 0 0 1 0 0 1
0 0 0 0 1 0 0 0 0 1]
[0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 1 1 0 0 0 1 0
1 0 0 0 0 0 0 1 1 0]
[0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 1 0 0
0 1 1 1 0 1 1 0 0 0]])
Got:
doctest:warning
File "<doctest
mdsage.kamiennys_criterion.KamiennyCriterion.?[4]>", line 1, in
<module>
C.verify_criterion(Integer(4))
File "/home/dima/software/sage-src/.venv/lib/python3.13/site-packages/mdsage/kamiennys_criterion.py",
line 1131, in verify_criterion
% (self.congruence_type, d, self.p, n, p, q, Kamienny_Version,
version()),
File "/home/dima/software/sage-src/.venv/lib/python3.13/site-packages/sage/misc/banner.py",
line 37, in version
deprecation(39015, "Use sage.version instead.")
File "/home/dima/software/sage-src/.venv/lib/python3.13/site-packages/sage/misc/superseded.py",
line 99, in deprecation
warning(issue_number, message, DeprecationWarning, stacklevel)
File "/home/dima/software/sage-src/.venv/lib/python3.13/site-packages/sage/misc/superseded.py",
line 180, in warning
warn(message, warning_class, stacklevel)
File "/usr/lib/python3.13/warnings.py", line 110, in _showwarnmsg
sw(msg.message, msg.category, msg.filename, msg.lineno,
:
DeprecationWarning: Use sage.version instead.
See https://github.com/sagemath/sage/issues/39015 for details.
(True,
'All conditions are satified for Gamma1 d=4 p=43. Using n=5,
modp=65521, q=3 in Kamienny Version 1.5 and SageMath version
10.8.beta2, Release Date: 2025-09-07',
[Vector space of degree 4 and dimension 0 over Finite Field of size 2
Basis matrix:
[],
Vector space of degree 23 and dimension 2 over Finite Field of size 2
Basis matrix:
[1 1 0 1 0 0 1 1 1 0 1 0 1 1 1 1 1 1 0 0 1 0 0]
[0 0 1 0 1 1 1 0 1 1 0 1 1 1 1 0 1 1 1 1 0 0 0],
Vector space of degree 42 and dimension 11 over Finite Field of size 2
Basis matrix:
[1 0 0 0 0 0 0 1 0 1 1 1 0 1 1 0 1 0 1 0 1 0 0 0 0 0 1 0 1 0 0 0
1 1 0 0 1 1 1 1 1 1]
[0 1 0 0 0 0 0 0 0 1 0 1 0 1 0 1 1 0 0 0 0 0 1 0 1 1 0 0 1 0 0 0
1 1 1 1 0 0 0 1 0 0]
[0 0 1 0 0 0 0 0 0 1 0 0 0 0 0 1 1 1 0 0 1 0 0 0 0 0 0 0 0 1 1 1
0 0 0 0 1 1 0 0 1 0]
[0 0 0 1 0 0 0 0 0 1 0 0 0 0 1 1 1 0 1 0 0 0 0 0 1 1 0 0 1 0 0 0
0 1 0 1 0 0 0 1 0 0]
[0 0 0 0 1 0 0 1 0 1 0 0 1 0 0 1 1 0 0 0 0 0 0 0 0 1 0 0 1 0 0 0
0 1 0 0 0 0 0 0 0 0]
[0 0 0 0 0 1 0 1 0 0 0 1 1 0 0 1 1 1 1 1 1 0 1 0 0 1 1 0 0 1 1 1
0 0 1 0 0 0 1 1 0 1]
[0 0 0 0 0 0 1 0 0 0 1 0 1 1 1 0 1 1 0 1 0 0 1 0 0 0 1 0 1 0 1 0
0 1 1 0 0 0 1 1 1 1]
[0 0 0 0 0 0 0 0 1 1 1 0 0 0 0 1 1 0 0 1 0 0 0 0 0 0 0 0 0 0 1 0
0 0 0 0 1 1 0 0 0 0]
[0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 0 1 0 0 0 1 0 0 1
0 0 0 0 1 0 0 0 0 1]
[0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 1 1 0 0 0 1 0
1 0 0 0 0 0 0 1 1 0]
[0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 1 0 0
0 1 1 1 0 1 1 0 0 0]])
**********************************************************************
1 item had failures:
1 of 12 in mdsage.kamiennys_criterion.KamiennyCriterion.?
[64 tests, 1 failure, 2.63s wall]
sage-runtests --warn-long 5.0
--random-seed=177091587185286457373292283220227525984
tmp/mdsage/mdsage/maartens_sage_functions.py
[28 tests, 0.31s wall]
sage-runtests --warn-long 5.0
--random-seed=177091587185286457373292283220227525984
tmp/mdsage/mdsage/modular_degrees_oldforms.py
[28 tests, 1.17s wall]
sage-runtests --warn-long 5.0
--random-seed=177091587185286457373292283220227525984
tmp/mdsage/mdsage/modular_unit_divisors.py
[2 tests, 0.01s wall]
sage-runtests --warn-long 5.0
--random-seed=177091587185286457373292283220227525984
tmp/mdsage/mdsage/one_cython_file.pyx
[4 tests, 0.01s wall]
sage-runtests --warn-long 5.0
--random-seed=177091587185286457373292283220227525984
tmp/mdsage/mdsage/quadratic_class_numbers.py
[17 tests, 0.91s wall]
sage-runtests --warn-long 5.0
--random-seed=177091587185286457373292283220227525984
tmp/mdsage/mdsage/ramification.py
[12 tests, 1.85s wall]
sage-runtests --warn-long 5.0
--random-seed=177091587185286457373292283220227525984
tmp/mdsage/mdsage/sage_bugs.py
[0 tests, 0.00s wall]
sage-runtests --warn-long 5.0
--random-seed=177091587185286457373292283220227525984
tmp/mdsage/mdsage/ultimate_question.py
[7 tests, 0.01s wall]
sage-runtests --warn-long 5.0
--random-seed=177091587185286457373292283220227525984
tmp/mdsage/mdsage/utilities.py
[12 tests, 0.19s wall]
----------------------------------------------------------------------
sage-runtests --warn-long 5.0
--random-seed=177091587185286457373292283220227525984
tmp/mdsage/mdsage/kamiennys_criterion.py # 1 doctest failed
----------------------------------------------------------------------
Total time for all tests: 10.5 seconds
cpu time: 9.8 seconds
cumulative wall time: 10.2 seconds
Features detected for doctesting:
(sage-src) dima@tarski ~/software/sage-src $

HTH
Dima

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[Maarten Derickx]

On Monday, 8 September 2025 at 08:35:49 UTC+2 Tobia...@gmx.de wrote:

Thanks for bringing this up!

>  what will be the recommended way to depend on sagemath in a pip package

As with any other python dependency: If you compile against sage (eg using cython), you should specify `sagemath` under `build-system > requires` in the pyproject.toml of your project. If sage is just a runtime dependency, then put it under `project > dependencies`.

Thanks. So slightly related to this. Does this mean that `sage -pip install sagemath==10.7` is going to be a supported way to update sagemath? I created a sample project having sagemath>=10.7 as a dependency. And doing `sage -pip install .` using sage 10.6 actually seems to have upgraded sage from 10.6 to 10.7. However doing the same for sage 10.5 or earlier seems to fail. In any case when starting to use sagemath more as a proper python dependency things like this will happen.

 

>  how to tell end users to install my pip package in an already working sage installation

Ideally, it would be like any other pip package: tell users to activate the venv they want to install it in, then run `pip install <your pip package>`. However, if you have sagemath declared as build requirement, then this might build sage again (if there is no cached wheel) since pip creates a new empty build env by default. To prevent that, one should use `pip install --no-build-isolation <your pip package>` in the sage venv. 

We should add some documentation for downstream sagemath packages.

Yes I would love this. There used to be  sage_sample for this: https://github.com/sagemath/sage_sample but that is horribly outdated as there is no pyproject.toml, and uses travis_ci . 

[Maarten Derickx]

Hi Dima,

First of all thanks for your quick response. Yes I agree that I need to update the way my package is build and installed most of the code in setup.py is over 8 years old. In fact that is why I started this question here, because I am unsure what are the best ways to do it. 

Also one addition is that I would like to state is. I would very much like to depend on a "recent enough sage version" in such a way that installing inside a to old sage version raises some form of error telling them to update sage. I relied on "sagemath.check_version" to do this. At the moment I feel that maybe inlining the code in 'sagemath.check_version" in my install script might be the best way forward.  I guess I could not do this check any rely more on the existing python infrastructure, and letting go of the idea of "a sagemath installation", and start to think more as sagemath the python library. But I don't really like the user experience of getting an error message that sagemath==10.7 failed to install inside an existing sage 10.5 installation.

Note that my package doesn't break the latest stable release (10.7) , this doesn't mean that I claim what the package does right now should still be supported in the future, but at least that I don't need to fix it right now.

(sage-dev) ~/sage$ ./sage
┌────────────────────────────────────────────────────────────────────┐
│ SageMath version 10.7, Release Date: 2025-08-09                    │
│ Using Python 3.12.11. Type "help()" for help.                      │
└────────────────────────────────────────────────────────────────────┘
sage:                                                                                                                                                                    
(sage-dev) ~/sage$ ./sage -pip show sagemath
WARNING: Package(s) not found: sagemath
(sage-dev) ~/sage$ sage
┌────────────────────────────────────────────────────────────────────┐
│ SageMath version 10.7, Release Date: 2025-08-09                    │
│ Using Python 3.12.11. Type "help()" for help.                      │
└────────────────────────────────────────────────────────────────────┘
sage: from sagemath.check_version import check_version
---------------------------------------------------------------------------
ModuleNotFoundError                       Traceback (most recent call last)
Cell In[1], line 1
----> 1 from sagemath.check_version import check_version

ModuleNotFoundError: No module named 'sagemath'

(sage-dev) ~/sage$ sage -pip install sagemath==1.3.0
Collecting sagemath==1.3.0
Installing collected packages: sagemath
Successfully installed sagemath-1.3.0
(sage-dev) ~/sage$ ./sage
┌────────────────────────────────────────────────────────────────────┐
│ SageMath version 10.7, Release Date: 2025-08-09                    │
│ Using Python 3.12.11. Type "help()" for help.                      │
└────────────────────────────────────────────────────────────────────┘
sage: from sagemath.check_version import check_version
sage: check_version(">=10.8")
/projects/e68a5dda-ac71-432d-99b7-c1bfecf6c804/miniforge3/envs/sage-dev/lib/python3.12/site-packages/sagemath/check_version.py:12: DeprecationWarning: Use sage.version instead.

See https://github.com/sagemath/sage/issues/39015 for details.

  installed_version = sage_version_function().replace(',','').split()[2]
---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
Cell In[2], line 1
----> 1 check_version(">=10.8")

File ~/miniforge3/envs/sage-dev/lib/python3.12/site-packages/sagemath/check_version.py:22, in check_version(version)
     20         version = version.replace('>=','')
     21         if parse_version(version) > parse_version(installed_version):
---> 22             raise ValueError("""\n******************************************************************\n
     23 Sage version (= %s) is older than the required one (= %s)\n
     24 ******************************************************************"""%(installed_version,version))
     25     elif version == '':
     26         pass

ValueError:
******************************************************************

Sage version (= 10.7) is older than the required one (= 10.8)

******************************************************************
sage: 

[Maarten Derickx]

Hi Dima,

Sorry, I misread your reply. Your reply was about having sage in a venv. I was thinking about sage from conda forge, or any of the other documented (non development) installs documented on https://doc.sagemath.org/html/en/installation/index.html . As I primarily care about a good user experience for people that are relatively new to python and don't know what a venv is, and managed to get a working sagemath installation on their system. Or don't even know how to install sagemath, but have access to sagemath installation at a university server or cocalc.

Actually looking at that, I can't even find a documented way to install sage inside a venv using pip, I guess that is why the "usual" was in quotes?  At least I got one to work by using conda forge to install the prerequisites and then run `pip install sagemath` inside a venv. That being said, I am really happy that it was actually rather easy to get the sagemath library working in a "system python" venv. I.e. one that was not created using `sage -python venv`. I remember this not being possible in the past and causing me a lot of headaches. So many thanks to the people who put in the hard work to make this possible.

I am still scratching my head on how to support both kind of sagemath installs. Because the venv install requires sagemath as a dependency in pyproject.toml. While having sagemath as a python dependency will have unexpected consequence while using a conda forge install (i.e. potentially upgrading sagemath in the conda forge environment, or failing with a non user friendly error that sagemath failed to build).

[Dima Pasechnik]

On September 8, 2025 5:31:06 PM CDT, Maarten Derickx <m.derick...@gmail.com> wrote:
>Hi Dima,
>
>Sorry, I misread your reply. Your reply was about having sage in a venv. I
>was thinking about sage from conda forge, or any of the other documented
>(non development) installs documented
>on https://doc.sagemath.org/html/en/installation/index.html . As I
>primarily care about a good user experience for people that are relatively
>new to python and don't know what a venv is, and managed to get a working
>sagemath installation on their system. Or don't even know how to install
>sagemath, but have access to sagemath installation at a university server
>or cocalc.
>
>Actually looking at that, I can't even find a documented way to install
>sage inside a venv using pip,

in the installation manual there is a meson section, where one can find an example on how to install sage in a uv-created venv.
(this assumes enough deps is available on the system in some way).

I guess that is why the "usual" was in
>quotes? At least I got one to work by using conda forge to install the
>prerequisites and then run `pip install sagemath` inside a venv. That being
>said, I am really happy that it was actually rather easy to get the
>sagemath library working in a "system python" venv. I.e. one that was not
>created using `sage -python venv`. I remember this not being possible in
>the past and causing me a lot of headaches. So many thanks to the people
>who put in the hard work to make this possible.
>
>I am still scratching my head on how to support both kind of sagemath
>installs. Because the venv install requires sagemath as a dependency in
>pyproject.toml. While having sagemath as a python dependency will have
>unexpected consequence while using a conda forge install (i.e. potentially
>upgrading sagemath in the conda forge environment, or failing with a non
>user friendly error that sagemath failed to build).

pip install --no-build-isolation .

will make sure that sage(math) won't be rebuilt.

You might like to have a look at
<https://github.com/sagemath/sage/pull/40765>
where we are tackling more or less precisely this.

Later,
Dima