maintains_relationships

maintains_relationships(data, other_df, column)

Function to help ensuring that set of values in selected column remains the same in both DataFrames. This helps to maintain referential integrity.

Parameters

data: PolarsLazyOrDataFrame

Dataframe after transformation

other_df: Union[pl.DataFrame, pl.LazyFrame]

Distant dataframe usually the one before transformation

column: str

Column to check for keys/ids

Returns

Name	Type	Description
	PolarsLazyOrDataFrame	The original polars DataFrame or LazyFrame when the check passes

Examples

>>> import polars as pl
>>> import pelage as plg
>>> initial_df = pl.DataFrame({"a": ["a", "b"]})
>>> final_df = pl.DataFrame({"a": ["a", "b"]})
>>> final_df.pipe(plg.maintains_relationships, initial_df, "a")
shape: (2, 1)
┌─────┐
│ a   │
│ --- │
│ str │
╞═════╡
│ a   │
│ b   │
└─────┘
>>> final_df = pl.DataFrame({"a": ["a"]})

>>> final_df.pipe(plg.maintains_relationships, initial_df, "a")
Traceback (most recent call last):
...
pelage.types.PolarsAssertError: Details
shape: (1, 2)
┌──────┬──────────┐
│ a    ┆ a_in_ref │
│ ---  ┆ ---      │
│ str  ┆ str      │
╞══════╪══════════╡
│ null ┆ b        │
└──────┴──────────┘
Error with the DataFrame passed to the check function:
--> Some values were removed from col 'a', see above!