feat(python): Add show methods to DataFrame and LazyFrame

[guilhem-dvr]

This adds a show method for both DataFrame and LazyFrame objects, taking inspiration from pyspark's show method and taking into account the requirements from @stinodego in #16534.

I choose to only expose config options that influence the result width's size, to mimic pyspark's truncate option.

I've provided tests, but I'm not super satisfied with them: they could break when changing the default display options. I was thinking of mocking Config, print and display_html, would that be okay?

[alexander-beedie]

I've provided tests, but I'm not super satisfied with them: they could break when changing the default display options. I was thinking of mocking Config, print and display_html, would that be okay?

No need to mockConfig; it can act as a decorator¹, so you could decorate your tests such that you explicitly set the Config to some known values (eg: the current defaults) and then you can modify the values away from these defaults inside the test 👍

There are a few other options it would be nice to expose as well, such as tbl_formatting, tbl_cell_alignment, tbl_cell_numeric_alignment, etc.

I'd also change the parameter name n to limit, and allow it to be None (but maintain the default of 5). This would allow the caller to print the entire table (eg: with no limit).

Footnotes

1. Config as a decorator:
   https://docs.pola.rs/api/python/stable/reference/config.html#use-as-a-decorator ↩

[codecov]

Codecov Report

Attention: Patch coverage is 62.96296% with 10 lines in your changes missing coverage. Please review.

Project coverage is 79.93%. Comparing base (4360f9d) to head (c841458).
Report is 103 commits behind head on main.

Files with missing lines	Patch %	Lines
py-polars/polars/lazyframe/frame.py	50.00%	6 Missing ⚠️
py-polars/polars/dataframe/frame.py	73.33%	3 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #19634      +/-   ##
==========================================
- Coverage   80.05%   79.93%   -0.13%     
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  Files        1532     1536       +4     
  Lines      210752   211721     +969     
  Branches     2442     2449       +7     
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+ Hits       168715   169230     +515     
- Misses      41482    41936     +454     
  Partials      555      555              

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[guilhem-dvr]

@alexander-beedie I've added all config options that impact the display format of a dataframe.

I was thinking of hiding the dataframe shape by default because I find it a bit irrelevant when showing a dataframe, usually you would know what is the shape of the frame you are working with. But with the limitless option and for the sake of consistency I think I will leave it visible.

[alexander-beedie]

@alexander-beedie I've added all config options that impact the display format of a dataframe.

Good stuff, will take a look.

I was thinking of hiding the dataframe shape by default because I find it a bit irrelevant when showing a dataframe, usually you would know what is the shape of the frame you are working with.

Not necessarily - if it's wide (so cols are truncated in the repr) or you've just filtered the data you won't know the shape; definitely want to keep it 👍