feat: add datacompy compare CLI with multi-backend support - #544
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rhaffar
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Aug 5, 2026
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Looks good Faisal, just a few comments - thanks for incorporating some of the changes I recommended from the last PR
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| if join_columns and on_index: | ||
| raise BadArgsError("--on and --on-index are mutually exclusive.") | ||
| if not join_columns and not on_index: | ||
| raise BadArgsError( | ||
| "--on is required. Specify at least one join column with --on COL, " | ||
| "or use --on-index with --backend pandas to join on the index." | ||
| ) |
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We do check for this in the Pandas compare code - wondering if we should just passthrough both args and let the compare throw the error instead?
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I think we should catch it in the CLI process since its separate from the non-CLI part of datacompy. Open to changing it if you think otherwise!
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Makes sense, this one is more of a personal preference thing so more than ok to catch it in the CLI 👍
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Thanks Raymond:
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Closes #530, Using this one in favour of #534
Adds a
datacompyconsole script so two datasets can be compared from a shell without writing a throwaway script, for ad hoc checks and for CI pipelines that run as shell tasks.Exit codes: 0 match, 1 mismatch or threshold exceeded, 2 error, 130 interrupt.
Supports the pandas, polars, Spark, and Snowflake backends over CSV, Parquet, and JSON.
Design notes:
parser.pyholds one declarativeOPTIONStable that drives both theargparseparser and theCompareconstructorkwargs. Adding a library keyword to the CLI is a single new row rather than two hand-maintained lists, andtests/cli/test_parser.pychecks every mapping against the real constructor signature via inspect.signature, so the two cannot silently drift.--on-indexbeing pandas only and--cast-column-names-lowernot applying to Snowflake, is data on the spec row rather than a validation branch.backends.pydefines aCLIBackendABC mirroring the existingBaseComparestrategy pattern. Each backend owns its session, loaders, and constructor