# pandas.Series.str.zfill

`Series.str.``zfill`(width)

  Pad strings in the Series/Index by prepending ‘0’ characters.

  Strings in the Series/Index are padded with ‘0’ characters on the left of the string to reach a total string length width. Strings in the Series/Index with length greater or equal to width are unchanged.

  Parameters:

  width : int

  > Minimum length of resulting string; strings with length less than width be prepended with ‘0’ characters.

  Returns: | Series/Index of objects

  See also

  `Series.str.rjust`
    Fills the left side of strings with an arbitrary character.
  `Series.str.ljust`
    Fills the right side of strings with an arbitrary character.
  `Series.str.pad`
    Fills the specified sides of strings with an arbitrary character.
  `Series.str.center`
    Fills boths sides of strings with an arbitrary character.

  Notes

  Differs from `str.zfill()` which has special handling for ‘+’/’-‘ in the string.

  Examples

      >>> s = pd.Series(['-1', '1', '1000', 10, np.nan])
      >>> s
      0      -1
      1       1
      2    1000
      3      10
      4     NaN
      dtype: object

  Note that `10` and `NaN` are not strings, therefore they are converted to `NaN`. The minus sign in `'-1'` is treated as a regular character and the zero is added to the left of it (`str.zfill()` would have moved it to the left). `1000` remains unchanged as it is longer than width.

      >>> s.str.zfill(3)
      0     0-1
      1     001
      2    1000
      3     NaN
      4     NaN
      dtype: object

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