polars.Expr.str.slice#

Expr.str.slice( offset: int | IntoExprColumn, length: int | IntoExprColumn | None = None, ) → Expr[source]#

Extract a substring from each string value.

Parameters:

offset: Start index. Negative indexing is supported.
length: Length of the slice. If set to None (default), the slice is taken to the end of the string.

Returns:

Expr: Expression of data type String.

Notes

Both the offset and length inputs are defined in terms of the number of characters in the (UTF8) string. A character is defined as a Unicode scalar value. A single character is represented by a single byte when working with ASCII text, and a maximum of 4 bytes otherwise.

Examples

>>> df = pl.DataFrame({"s": ["pear", None, "papaya", "dragonfruit"]})
>>> df.with_columns(pl.col("s").str.slice(-3).alias("slice"))
shape: (4, 2)
┌─────────────┬───────┐
│ s           ┆ slice │
│ ---         ┆ ---   │
│ str         ┆ str   │
╞═════════════╪═══════╡
│ pear        ┆ ear   │
│ null        ┆ null  │
│ papaya      ┆ aya   │
│ dragonfruit ┆ uit   │
└─────────────┴───────┘

Using the optional length parameter

>>> df.with_columns(pl.col("s").str.slice(4, length=3).alias("slice"))
shape: (4, 2)
┌─────────────┬───────┐
│ s           ┆ slice │
│ ---         ┆ ---   │
│ str         ┆ str   │
╞═════════════╪═══════╡
│ pear        ┆       │
│ null        ┆ null  │
│ papaya      ┆ ya    │
│ dragonfruit ┆ onf   │
└─────────────┴───────┘