polars_plan/dsl/functions/
selectors.rs

1use super::*;
2
3/// Create a Column Expression based on a column name.
4///
5/// # Arguments
6///
7/// * `name` - A string slice that holds the name of the column. If a column with this name does not exist when the
8///   LazyFrame is collected, an error is returned.
9///
10/// # Examples
11///
12/// ```ignore
13/// // select a column name
14/// col("foo")
15/// ```
16///
17/// ```ignore
18/// // select all columns by using a wildcard
19/// col("*")
20/// ```
21///
22/// ```ignore
23/// // select specific columns by writing a regular expression that starts with `^` and ends with `$`
24/// // only if regex features is activated
25/// col("^foo.*$")
26/// ```
27pub fn col<S>(name: S) -> Expr
28where
29    S: Into<PlSmallStr>,
30{
31    let name = name.into();
32    match name.as_str() {
33        "*" => Expr::Wildcard,
34        _ => Expr::Column(name),
35    }
36}
37
38/// Selects all columns. Shorthand for `col("*")`.
39pub fn all() -> Expr {
40    Expr::Wildcard
41}
42
43/// Select multiple columns by name.
44pub fn cols<I, S>(names: I) -> Expr
45where
46    I: IntoIterator<Item = S>,
47    S: Into<PlSmallStr>,
48{
49    let names = names.into_iter().map(|x| x.into()).collect();
50    Expr::Columns(names)
51}
52
53/// Select multiple columns by dtype.
54pub fn dtype_col(dtype: &DataType) -> Expr {
55    Expr::DtypeColumn(vec![dtype.clone()])
56}
57
58/// Select multiple columns by dtype.
59pub fn dtype_cols<DT: AsRef<[DataType]>>(dtype: DT) -> Expr {
60    let dtypes = dtype.as_ref().to_vec();
61    Expr::DtypeColumn(dtypes)
62}
63
64/// Select multiple columns by index.
65pub fn index_cols<N: AsRef<[i64]>>(indices: N) -> Expr {
66    let indices = indices.as_ref().to_vec();
67    Expr::IndexColumn(Arc::from(indices))
68}
polars_plan/dsl/functions/selectors.rs

polars_plan/dsl/functions/
selectors.rs
