fix(python, rust): properly interpret FMT_MAX_ROWS - remove arbitrary minimum, fix Series formatting

[alexander-beedie]

Some slightly OCD updates/fixes:

• Fixed a few issues with use of FMT_MAX_ROWS (Rust)

  • Removed arbitrary minimum value:

    Min value was forcibly capped at 2, due to the formatting code requiring at least one row before and one row after any ... placeholders (which represent extant but non-displayed rows/cells); adjusted things so it properly handles 0 and 1.

    Not many compelling reasons to want to set such small values, but equally there are no good reasons not to allow it if somebody decides they do want to :)

    # -----------------+------------------------------------
    # BEFORE           | AFTER 
    # (1/0 fmt like 2) | (1/0 format as expected)
    # -----------------+------------------------------------
    #                  |
    # shape: (3, 2)    |    shape: (3, 2)    shape: (3, 2)  
    # ┌─────┬─────┐    |    ┌─────┬─────┐    ┌─────┬─────┐
    # │ s   ┆ n   │    |    │ s   ┆ n   │    │ s   ┆ n   │
    # │ --- ┆ --- │    |    │ --- ┆ --- │    │ --- ┆ --- │
    # │ str ┆ i64 │    |    │ str ┆ i64 │    │ str ┆ i64 │
    # ╞═════╪═════╡    |    ╞═════╪═════╡    ╞═════╪═════╡
    # │ a   ┆ 1   │    |    │ a   ┆ 1   │    │ ... ┆ ... │
    # ├╌╌╌╌╌┼╌╌╌╌╌┤    |    ├╌╌╌╌╌┼╌╌╌╌╌┤    └─────┴─────┘
    # │ ... ┆ ... │    |    │ ... ┆ ... │
    # ├╌╌╌╌╌┼╌╌╌╌╌┤    |    └─────┴─────┘
    # │ c   ┆ 3   │    |
    # └─────┴─────┘    |

  • Fixed Series formatting for certain values:

    Certain values of FMT_MAX_ROWS resulted in incorrect formatting (omitting a value), due to integer division shenanigans; wasn't previously noticed as the default is a small even number. Fixed the array formatting macro that calculates what to display (in addition to also handling 0 and 1 values, as above).

    Example: when FMT_MAX_ROWS = 3 →

    # ---------------------------------------+----------------------
    # BEFORE                                 |  AFTER 
    # (df is correct)  (series missing "3")  |  (series matches df)
    # ---------------------------------------+----------------------
    #                                        |
    # shape: (4, 1)     shape: (4,)          |   shape: (4,)
    # ┌─────┐           Series: 'n' [i64]    |   Series: 'n' [i64]
    # │ n   │           [                    |   [ 
    # │ --- │               1                |       1 
    # │ i64 │               ...              |       ...
    # ╞═════╡               4                |       3
    # │ 1   │           ]                    |       4
    # │ ... │                                |   ]
    # │ 3   │                                |
    # │ 4   │                                |
    # └─────┘                                |

• Consolidated config vars (Rust)

  Noticed that there is an existing config.rs, but it was never updated with the newer table formatting variables; updated accordingly so we don't have a mix of bare strings and const refs.

• Exposed new UTF_FULL_CONDENSED comfy-table preset (Rust, Python)
  (which I added there earlier in the week to help reclaim some vertical space ;)

  >>> pl.Config.set_tbl_formatting("UTF8_FULL_CONDENSED")
  
  # UTF_FULL:            UTF_FULL_CONDENSED:
  # ┌───────┬───────┐    ┌───────┬───────┐
  # │ Hello ┆ there │    │ Hello ┆ there │
  # ╞═══════╪═══════╡    ╞═══════╪═══════╡
  # │ a     ┆ b     │    │ a     ┆ b     │
  # ├╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌┤    │ c     ┆ d     │
  # │ c     ┆ d     │    │ e     ┆ f     │
  # ├╌╌╌╌╌╌╌┼╌╌╌╌╌╌╌┤    └───────┴───────┘
  # │ e     ┆ f     │ 
  # └───────┴───────┘    

• Misc: fixed Expr docstring examples for round and truncate (Python)
  The examples in these two expressions were directly copied from Series instead of actually showing the relevant expressions in use; updated appropriately.

[alexander-beedie]

Looks like a few doctests need updating as a result of fixing Series formatting...

Updated: done.

[ghuls]

@alexander-beedie comfy-table version is also updated a few days ago in Polars, so it is possible that there is more useful stuff in the 6.x release: https://github.com/Nukesor/comfy-table/blob/main/CHANGELOG.md

[alexander-beedie]

@alexander-beedie comfy-table version is also updated a few days ago in Polars, so it is possible that there is more useful stuff in the 6.x release: https://github.com/Nukesor/comfy-table/blob/main/CHANGELOG.md

Yup, I'm curious if there's anything else we can do with it...
(I saw you'd already taken advantage of the new add_rows method :)