class_docstr: Namespace for string related expressions.
class_docstr_tok: ["Namespace","for","string","related","expressions","."]
docstr: Pad the start of the string with zeros until it reaches the given length.
  
  A sign prefix (`-`) is handled by inserting the padding after the sign
  character rather than before.
  
  Parameters
  ----------
  length
      Pad the string until it reaches this length. Strings with length equal to
      or greater than this value are returned as-is.
  
  See Also
  --------
  pad_start
  
  Notes
  -----
  This method is intended for padding numeric strings. If your data contains
  non-ASCII characters, use :func:`pad_start` instead.
  
  Examples
  --------
  >>> df = pl.DataFrame({"a": [-1, 123, 999999, None]})
  >>> df.with_columns(zfill=pl.col("a").cast(pl.String).str.zfill(4))
  shape: (4, 2)
  ┌────────┬────────┐
  │ a      ┆ zfill  │
  │ ---    ┆ ---    │
  │ i64    ┆ str    │
  ╞════════╪════════╡
  │ -1     ┆ -001   │
  │ 123    ┆ 0123   │
  │ 999999 ┆ 999999 │
  │ null   ┆ null   │
  └────────┴────────┘
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code: def zfill(self, length: int) -> Expr:
      """
      Pad the start of the string with zeros until it reaches the given length.
  
      A sign prefix (`-`) is handled by inserting the padding after the sign
      character rather than before.
  
      Parameters
      ----------
      length
          Pad the string until it reaches this length. Strings with length equal to
          or greater than this value are returned as-is.
  
      See Also
      --------
      pad_start
  
      Notes
      -----
      This method is intended for padding numeric strings. If your data contains
      non-ASCII characters, use :func:`pad_start` instead.
  
      Examples
      --------
      >>> df = pl.DataFrame({"a": [-1, 123, 999999, None]})
      >>> df.with_columns(zfill=pl.col("a").cast(pl.String).str.zfill(4))
      shape: (4, 2)
      ┌────────┬────────┐
      │ a      ┆ zfill  │
      │ ---    ┆ ---    │
      │ i64    ┆ str    │
      ╞════════╪════════╡
      │ -1     ┆ -001   │
      │ 123    ┆ 0123   │
      │ 999999 ┆ 999999 │
      │ null   ┆ null   │
      └────────┴────────┘
  
      """
      return wrap_expr(self._pyexpr.str_zfill(length))
  
imports: from __future__ import annotations
  import warnings
  from typing import TYPE_CHECKING
  import polars._reexport
  from polars import functions
  from polars.datatypes import Date, Datetime, Int32, Time, py_type_to_dtype
  from polars.exceptions import ChronoFormatWarning
  from polars.utils._parse_expr_input import parse_as_expression
  from polars.utils._wrap import wrap_expr
  from polars.utils.deprecation import deprecate_renamed_function, deprecate_renamed_parameter, rename_use_earliest_to_ambiguous
  from polars.utils.various import find_stacklevel
label_desc: Use image node_id 20 for calling the ExprStringNameSpace obj's underlying member method code with example usage: obj.zfill(length) and returns: wrap_expr