Add support for Template type (t-strings) to pprint

[loic-simon]

Feature or enhancement

Proposal:

Update pprint functions to understand and format Template and Interpolation types:

>>> from pprint import pp
>>> name = "World"
>>> pp(t"Hello {World}")
Template(strings=('Hello ', ''),
         interpolations=(Interpolation('World', 'name', None, ''),))""")

I believe it will be quite common to play with t-strings in the REPL and other dynamic environments, where pretty formatting could help a lot. I don't know how high is the bar for adding types to the pprint registry, though.

If this is deemed worthwhile, I have a working implementation, pretty straightforward.

---

More complex examples (inspired from the PEP), to give a sense of what it could look like:

>>> attributes = {"id": "main"}
>>> attribute_value = "shrubbery"
>>> content = "hello"
>>> template = t"<span {attributes} data-value={attribute_value}>{content}</span>"
>>> pp(template)
Template(strings=('<span ', ' data-value=', '>', '</span>'),
         interpolations=(Interpolation({'id': 'main'}, 'attributes', None, ''),
                         Interpolation('shrubbery',
                                       'attribute_value',
                                       None,
                                       ''),
                         Interpolation('hello', 'content', None, '')))
>>>
>>> nested = t"<div>{template}</div>"
>>> pp(nested)
Template(strings=('<div>', '</div>'),
         interpolations=(Interpolation(Template(strings=('<span ',
                                                         ' data-value=',
                                                         '>',
                                                         '</span>'),
                                                interpolations=(Interpolation({'id': 'main'},
                                                                              'attributes',
                                                                              None,
                                                                              ''),
                                                                Interpolation('shrubbery',
                                                                              'attribute_value',
                                                                              None,
                                                                              ''),
                                                                Interpolation('hello',
                                                                              'content',
                                                                              None,
                                                                              ''))),
                                       'template',
                                       None,
                                       ''),))

Unfortunately, "interpolation" being a quite long word repeated 2 times in the repr of a t-string, with default formatting rules we soon have text crumpled to the right of the screen... but I believe it is still more readable than

Template(strings=('<div>', '</div>'), interpolations=(Interpolation(Template(strings=('<span ', ' da
ta-value=', '>', '</span>'), interpolations=(Interpolation({'id': 'main'}, 'attributes', None, ''),  
Interpolation('shrubbery', 'attribute_value', None, ''), Interpolation('hello', 'content', None, '')
)), 'template', None, ''),))

Has this already been discussed elsewhere?

This is a minor feature, which does not need previous discussion elsewhere

Links to previous discussion of this feature:

No response

Linked PRs

• gh-134551: Add t-strings support to pprint #134577

[hugovk]

Good idea, cc @davepeck @lysnikolaou

---

More complex examples (inspired from the PEP), to give a sense of what it could look like:

>>> attributes = {"id": "main"}
>>> attribute_value = "shrubbery"
>>> content = "hello"
>>> template = t"<span {attributes} data-value={attribute_value}>{content}</span>"
>>> pp(template)
Template(strings=('<span ', ' data-value=', '>', '</span>'),
         interpolations=(Interpolation({'id': 'main'}, 'attributes', None, ''),
                         Interpolation('shrubbery',
                                       'attribute_value',
                                       None,
                                       ''),
                         Interpolation('hello', 'content', None, '')))
>>>
>>> nested = t"<div>{template}</div>"
>>> pp(nested)
Template(strings=('<div>', '</div>'),
         interpolations=(Interpolation(Template(strings=('<span ',
                                                         ' data-value=',
                                                         '>',
                                                         '</span>'),
                                                interpolations=(Interpolation({'id': 'main'},
                                                                              'attributes',
                                                                              None,
                                                                              ''),
                                                                Interpolation('shrubbery',
                                                                              'attribute_value',
                                                                              None,
                                                                              ''),
                                                                Interpolation('hello',
                                                                              'content',
                                                                              None,
                                                                              ''))),
                                       'template',
                                       None,
                                       ''),))

Or something like Black formatting takes up less vertical and horizontal space:

Template(
    strings=("<div>", "</div>"),
    interpolations=(
        Interpolation(
            Template(
                strings=("<span ", " data-value=", ">", "</span>"),
                interpolations=(
                    Interpolation({"id": "main"}, "attributes", None, ""),
                    Interpolation("shrubbery", "attribute_value", None, ""),
                    Interpolation("hello", "content", None, ""),
                ),
            ),
            "template",
            None,
            "",
        ),
    ),
)

And taking the simpler case:

>>> from pprint import pp
>>> name = "World"
>>> pp(t"Hello {World}")
Template(strings=('Hello ', ''),
         interpolations=(Interpolation('World', 'name', None, ''),))""")

Formats like:

Template(
    strings=("Hello ", ""), interpolations=(Interpolation("World", "name", None, ""))
)

Or with --line-length 79 uses more vertical space but feels more readable:

Template(
    strings=("Hello ", ""),
    interpolations=(Interpolation("World", "name", None, ""),),
)

Obviously we don't need to implement the full flexibility and complexity of Black-style formatting, but perhaps something along these lines?

[loic-simon]

Or something like Black formatting takes up less vertical and horizontal space:

I didn't dare to get away from pprint conventions (that follow PEP8, if I'm not mistaken) 😄 but I agree it would be way more readeable!

[lysnikolaou]

I agree with @hugovk that Black-like formatting makes this more readable. If people are okay with that, I'd certainly prefer it.