cast

ColExpr.cast(

target_type: Dtype | type,

*,

strict: bool = True,

) → Cast

Cast to a different data type.

Parameters:

target_type – The type to cast to.

The following casts are possible:

Input type	Target type	Note
Float	Int8, Int16, Int32, Int64	Extracts the integer part (i.e. rounds towards 0).
String	Int8, Int16, Int32, Int64	Parses the string as an integer.
String	Float32, Float64	Parses the string as a floating point number.
Int	String	Writes the integer in base 10 as a string.
Float	String	Writes the floating point number in decimal notation in base 10.
Int	Int8, Int16, Int32, Int64	Casts to an integer with a specified number of bits. Behavior is backend-dependent.
Float	Float32, Float64	Casts to a floating point number with a specified number of bits. Behavior is backend-dependent.
Datetime	Date	Removes the time component of the Datetime.
Datetime	String	Writes the datetime in the format YYYY-MM-DD HH:MM:SS.SSSSSS. Seconds are printed up to microsecond resolution.
Date	String	Writes the date in the format YYYY-MM-DD.

In addition to these casts, there are implicit conversion of integers to floating point numbers and dates to datetimes. They happens automatically and do not require an explicit cast.

Note

In casts from strings, neither leading nor trailing whitespace is allowed.

Examples

>>> t = pdt.Table({"a": [3.5, 10.3, -434.4, -0.2]}, name="T")
>>> t >> mutate(b=t.a.cast(pdt.Int32())) >> show()
Table T, backend: PolarsImpl
shape: (4, 2)
┌────────┬──────┐
│ a      ┆ b    │
│ ---    ┆ ---  │
│ f64    ┆ i32  │
╞════════╪══════╡
│ 3.5    ┆ 3    │
│ 10.3   ┆ 10   │
│ -434.4 ┆ -434 │
│ -0.2   ┆ 0    │
└────────┴──────┘