pandas.errors.MergeError — pandas 3.0.0.dev0+2098.g9c5b9ee823 documentation (original) (raw)

exception pandas.errors.MergeError[source]#

Exception raised when merging data.

Subclass of ValueError.

See also

DataFrame.join

For joining DataFrames on their indexes.

merge

For merging two DataFrames on a common set of keys.

Examples

left = pd.DataFrame( ... {"a": ["a", "b", "b", "d"], "b": ["cat", "dog", "weasel", "horse"]}, ... index=range(4), ... ) right = pd.DataFrame( ... {"a": ["a", "b", "c", "d"], "c": ["meow", "bark", "chirp", "nay"]}, ... index=range(4), ... ).set_index("a") left.join( ... right, ... on="a", ... validate="one_to_one", ... ) Traceback (most recent call last): MergeError: Merge keys are not unique in left dataset; not a one-to-one merge