proper polymake preferences, perhaps using Python 'with'

[mkoeppe]

Following up on #22452 (Create a Polymake pexpect interface):

Polymake's prefer is bad because it is too persistent, writing to a preference file.
We cannot use prefer_now directly because it is local to the current line.
We should have a way to set preferences local to a code block.
Perhaps a Python context manager (using the with keyword) would be the right solution.

See also: #22710: Meta-ticket: polymake

Depends on #22452

CC: @simon-king-jena

Component: interfaces

Keywords: days84

Issue created by migration from https://trac.sagemath.org/ticket/22703

[simon-king-jena]

Replying to @mkoeppe:

Polymake's prefer is bad because it is too persistent, writing to a preference file.
We cannot use prefer_now directly because it is local to the current line.
We should have a way to set preferences local to a code block.
Perhaps a Python context manager (using the with keyword) would be the right solution.

I agree that we don't want Sage to set preferences permanently (unless the user asks it). Although a "with" block may be a good solution for modules, I don't think that we want that in an interactive session.

So, I think ideally we would have a method polymake.preferences, so that

sage: polymake.preferences(...)

would set preferences that expire when the sage session ends, and

with polymake.preferences(...):
    many
    lines
    of
    code

would set preferences that expire when the "with" block ends.

[mkoeppe]

Description changed:

--- 
+++ 
@@ -1,4 +1,8 @@
+Following up on #22452 (Create a Polymake pexpect interface):
+
 Polymake's `prefer` is bad because it is too persistent, writing to a preference file.
 We cannot use `prefer_now` directly because it is local to the current line.
 We should have a way to set preferences local to a code block.
 Perhaps a Python context manager (using the `with` keyword) would be the right solution.
+
+See also: #22710: Meta-ticket: polymake

[mkoeppe]

Dependencies: #22452