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# pandas.errors.MergeError

exception pandas.errors.MergeError

  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