printing: Remove curly braces from subscripted variables in python() and pycode()

[AaronStiff]

References to other Issues or PRs

Fixes #20762

Brief description of what is fixed or changed

Added handling for subscripted variables in python and pycode. Subscripted variables only become an issue when using a parsed latex expression, since latex wraps them in curly braces. python and pycode were creating variable names with curly braces in them, resulting in syntax errors. Added a simple check and modification in python, but redefined inherited _print_Symbol in pycode's PythonCodePrinter.

Other comments

Release Notes

• printing
  • Remove curly braces from subscripted variables in python() and pycode()

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• printing
  • Remove curly braces from subscripted variables in python() and pycode() (#20806 by @AaronStiff and @oscargus)

This will be added to https://github.com/sympy/sympy/wiki/Release-Notes-for-1.10.

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Fixes #20762 

#### Brief description of what is fixed or changed
Added handling for subscripted variables in `python` and `pycode`. Subscripted variables only become an issue when using a parsed latex expression, since latex wraps them in curly braces. `python` and `pycode` were creating variable names with curly braces in them, resulting in syntax errors. Added a simple check and modification in `python`, but redefined inherited `_print_Symbol` in `pycode`'s `PythonCodePrinter`.

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* printing
    * Remove curly braces from subscripted variables in python() and pycode()
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Update

The release notes on the wiki have been updated.

[AaronStiff]

Where should I put the tests for this? They require antlr, which doesn't get imported in test_pycode.py or test_python.py.

[oscargus]

Where should I put the tests for this?

Either you check for it in the test, something like

antlr4 = import_module("antlr4")

# disable tests if antlr4-python*-runtime is not present
if not antlr4:
    disabled = True

so import antlr in the test and check if it is present, if not just return.

Or you may put the test in https://github.com/sympy/sympy/blob/master/sympy/parsing/tests/test_latex.py (where the code above is borrowed from).

[oscargus]

What about newsymbolname = symbolname.replace('{', '').replace('}', '')?

[AaronStiff]

Woah, I haven't touched sympy for half a year! :)

Would you mind taking over here?

[oscargus]

Sure, I can probably give it a go. Seems like it is just to sort out the test aspect (and possibly rewrite using replace).

[oscargus]

Couldn't figure out how to easily get your repo to my local computer so went for the "edit on GitHub"-approach. Not a brilliant idea in hindsight, but hopefully it will pass...

[github-actions]

Benchmark results from GitHub Actions

Lower numbers are good, higher numbers are bad. A ratio less than 1
means a speed up and greater than 1 means a slowdown. Green lines
beginning with + are slowdowns (the PR is slower then master or
master is slower than the previous release). Red lines beginning
with - are speedups.

Significantly changed benchmark results (PR vs master)

Significantly changed benchmark results (master vs previous release)

Full benchmark results can be found as artifacts in GitHub Actions
(click on checks at the top of the PR).

[oscarbenjamin]

Couldn't figure out how to easily get your repo to my local computer so went for the "edit on GitHub"-approach. Not a brilliant idea in hindsight, but hopefully it will pass...

My approach to doing this is twofold. To check out a PR I have the following in .git/config:

[remote "upstream"]
  url = https://github.com/sympy/sympy.git
  fetch = +refs/heads/*:refs/remotes/upstream/*
  fetch = +refs/pull/*/head:refs/remotes/upstream/pr/*
  pushurl = no_push

With that I can do git fetch upstream and then any PR is available as git checkout upsteram/pr/12345.

Then if I want to make changes and push to the PR it's:

git checkout upstream/pr/20806
# make changes
git commit -am 'message'
git push git@github.com:AaronStiff/sympy.git HEAD:issues/20762-python-printing-subscripts

The username and branch name are taken from the header of the webpage in the PR on GitHub