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Per discussion on
[Discord](https://discord.com/channels/601130461678272522/864228801851949077/1265718178927870045)
# Description
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To facilitate column-oriented dataframe construction, this PR added a
`--as-columns` flag to `polars into-df` command so that when specified,
and when input shape is record of lists, each list will be treated as a
column rather than a cell value, i.e. `{a: [1 3], b: [2 4]} | polars
into-df --as-columns` returns the same dataframe as `[[a b];[1 2] [3 4]]
| polars into-df`
# User-Facing Changes
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A new flag `--as-columns`, no change of semantics if this flag is
unspecified.
# Tests + Formatting
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# After Submitting
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---------
Co-authored-by: Ben Yang <ben@ya.ng>
12f57dbc62