# dask.dataframe.Index.fillna

Index.fillna(value=None, method=None, limit=None, axis=None)

  Fill NA/NaN values using the specified method.

  This docstring was copied from pandas.core.frame.DataFrame.fillna.

  Some inconsistencies with the Dask version may exist.

  Parameters:
    value scalar, dict, Series, or DataFrame

      Value to use to fill holes (e.g. 0), alternately a dict/Series/DataFrame of values specifying which value to use for each index (for a Series) or column (for a DataFrame). Values not in the dict/Series/DataFrame will not be filled. This value cannot be a list.

    method{‘backfill’, ‘bfill’, ‘ffill’, None}, default None

      Method to use for filling holes in reindexed Series:

      - ffill: propagate last valid observation forward to next valid.

      - backfill / bfill: use next valid observation to fill gap.

      Deprecated since version 2.1.0: Use ffill or bfill instead.

    axis{0 or ‘index’} for Series, {0 or ‘index’, 1 or ‘columns’} for DataFrame

      Axis along which to fill missing values. For Series this parameter is unused and defaults to 0.

    inplace bool, default False (Not supported in Dask)

      If True, fill in-place. Note: this will modify any other views on this object (e.g., a no-copy slice for a column in a DataFrame).

    limit int, default None

      If method is specified, this is the maximum number of consecutive NaN values to forward/backward fill. In other words, if there is a gap with more than this number of consecutive NaNs, it will only be partially filled. If method is not specified, this is the maximum number of entries along the entire axis where NaNs will be filled. Must be greater than 0 if not None.

    downcast dict, default is None (Not supported in Dask)

      A dict of item->dtype of what to downcast if possible, or the string ‘infer’ which will try to downcast to an appropriate equal type (e.g. float64 to int64 if possible).

      Deprecated since version 2.2.0.

  Returns:
    Series/DataFrame or None

      Object with missing values filled or None if `inplace=True`.

  See also

  `ffill`

    Fill values by propagating the last valid observation to next valid.

  `bfill`

    Fill values by using the next valid observation to fill the gap.

  `interpolate`

    Fill NaN values using interpolation.

  `reindex`

    Conform object to new index.

  `asfreq`

    Convert TimeSeries to specified frequency.

  Examples

      >>> df = pd.DataFrame([[np.nan, 2, np.nan, 0],
      ...                    [3, 4, np.nan, 1],
      ...                    [np.nan, np.nan, np.nan, np.nan],
      ...                    [np.nan, 3, np.nan, 4]],
      ...                   columns=list("ABCD"))
      >>> df
           A    B   C    D
      0  NaN  2.0 NaN  0.0
      1  3.0  4.0 NaN  1.0
      2  NaN  NaN NaN  NaN
      3  NaN  3.0 NaN  4.0

  Replace all NaN elements with 0s.

      >>> df.fillna(0)
           A    B    C    D
      0  0.0  2.0  0.0  0.0
      1  3.0  4.0  0.0  1.0
      2  0.0  0.0  0.0  0.0
      3  0.0  3.0  0.0  4.0

  Replace all NaN elements in column ‘A’, ‘B’, ‘C’, and ‘D’, with 0, 1, 2, and 3 respectively.

      >>> values = {"A": 0, "B": 1, "C": 2, "D": 3}
      >>> df.fillna(value=values)
           A    B    C    D
      0  0.0  2.0  2.0  0.0
      1  3.0  4.0  2.0  1.0
      2  0.0  1.0  2.0  3.0
      3  0.0  3.0  2.0  4.0

  Only replace the first NaN element.

      >>> df.fillna(value=values, limit=1)
           A    B    C    D
      0  0.0  2.0  2.0  0.0
      1  3.0  4.0  NaN  1.0
      2  NaN  1.0  NaN  3.0
      3  NaN  3.0  NaN  4.0

  When filling using a DataFrame, replacement happens along the same column names and same indices

      >>> df2 = pd.DataFrame(np.zeros((4, 4)), columns=list("ABCE"))
      >>> df.fillna(df2)
           A    B    C    D
      0  0.0  2.0  0.0  0.0
      1  3.0  4.0  0.0  1.0
      2  0.0  0.0  0.0  NaN
      3  0.0  3.0  0.0  4.0

  Note that column D is not affected since it is not present in df2.