Gallery example "choropleth map": Use code block separator "# %%"

[yvonnefroehlich]

Description of proposed changes

Related to PR #2662, this PR aims to use the code block separator # %% in the gallery example "Choropleth map".

Reminders

• Run make format and make check to make sure the code follows the style guide.
• Add tests for new features or tests that would have caught the bug that you're fixing.
• Add new public functions/methods/classes to doc/api/index.rst.
• Write detailed docstrings for all functions/methods.
• If wrapping a new module, open a 'Wrap new GMT module' issue and submit reasonably-sized PRs.
• If adding new functionality, add an example to docstrings or tutorials.
• Use underscores (not hyphens) in names of Python files and directories.

Slash Commands

You can write slash commands (/command) in the first line of a comment to perform
specific operations. Supported slash commands are:

• /format: automatically format and lint the code
• /test-gmt-dev: run full tests on the latest GMT development version

[seisman]

perhaps we should add a check to make sure that examples must have at least one # %% separators

[yvonnefroehlich]

perhaps we should add a check to make sure that examples must have at least one # %% separators

If this is something that can be added easily, I feel we should add such a check, as it's likely that we'll forget adding #%% also in upcoming examples. But if this is more complicated, I am not sure whether the effort is worth it.

[weiji14]

perhaps we should add a check to make sure that examples must have at least one # %% separators

If this is something that can be added easily, I feel we should add such a check, as it's likely that we'll forget adding #%% also in upcoming examples. But if this is more complicated, I am not sure whether the effort is worth it.

Could try to find a regex statement that checks for the presence of at least one # %% in the examples/**/*.py files, and add it to https://github.com/GenericMappingTools/pygmt/blob/v0.10.0/.github/workflows/style_checks.yaml? Or just add it under Reminders in the PR template.

[seisman]

Could try to find a regex statement that checks for the presence of at least one # %% in the examples/**/*.py files, and add it to https://github.com/GenericMappingTools/pygmt/blob/v0.10.0/.github/workflows/style_checks.yaml?

This one-line command can be used to detect example files that don't have # %%:

grep -L '# %%' $(find examples -name '*.py')