physics.quantum: Respect local printer settings in _sympystr.

[eric-wieser]

Calling sstr, str, or "%s" % inside _sympystr discards local printer settings and uses the global ones.
It also means subclasses of sympy.printing.str.StrPrinter are ignored.

References to other Issues or PRs

Brief description of what is fixed or changed

Other comments

Release Notes

• physics.quantum
  • When printing, Commutator, Anticommutator, InnerProduct, TensorProduct, and OuterProduct now respect keyword-arguments to sstr.

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• physics.quantum
  • When printing, Commutator, Anticommutator, InnerProduct, TensorProduct, and OuterProduct now respect keyword-arguments to sstr. (#19424 by @eric-wieser)

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Calling `sstr`, `str`, or `"%s" %` inside `_sympystr` discards local printer settings and uses the global ones.
It also means subclasses of `sympy.printing.str.StrPrinter` are ignored.

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#### Brief description of what is fixed or changed


#### Other comments


#### Release Notes

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<!-- BEGIN RELEASE NOTES -->
* physics.quantum
  * When printing, `Commutator`, `Anticommutator`, `InnerProduct`, `TensorProduct`, and `OuterProduct` now respect keyword-arguments to `sstr`.
<!-- END RELEASE NOTES -->

Update

The release notes on the wiki have been updated.

[codecov]

Codecov Report

Merging #19424 into master will increase coverage by 0.007%.
The diff coverage is 100.000%.

@@              Coverage Diff              @@
##            master    #19424       +/-   ##
=============================================
+ Coverage   75.611%   75.618%   +0.007%     
=============================================
  Files          652       652               
  Lines       169634    169684       +50     
  Branches     40032     40049       +17     
=============================================
+ Hits        128263    128313       +50     
- Misses       35758     35760        +2     
+ Partials      5613      5611        -2     

[oscarbenjamin]

Are there any examples where the output is changed as a result of these changes?

[eric-wieser]

Yes, any call of sstr(obj, **kw) where kw contains keys from StrPrinter._default_settings that have a visible effect.

[oscarbenjamin]

Can you give an example (in code)?

I often look at the added tests as a starting point to understand the effect of the changes in a PR. This doesn't add or change any tests though.

[eric-wieser]

This is one of those cases where it's a lot easier to see that the logic is wrong than it is to construct the corner case when it matters.

Here's the one I came up with:

from sympy import symbols, sstr
from sympy.physics.quantum import AntiCommutator
from sympy.physics.quantum import Operator
x, y = symbols('x,y')
A = Operator('A')
B = Operator('B')
sstr(AntiCommutator(A, B + 1.0), full_prec=True)
# before: '{1.0 + B,AA}'
# after: '{1.00000000000000 + B,AA}'

[oscarbenjamin]

Okay, thanks. I would suggest adding that as a test but I'm not sure if the object makes sense mathematically.