Selection trait accept String slice

polars/src/frame/group_by.rs

@@ -162,7 +162,7 @@ impl DataFrame {
     ///     .sum()
     /// }
     /// ```
-    pub fn groupby<'g, S: Selection<'g>>(&self, by: S) -> Result<GroupBy> {
+    pub fn groupby<'g, J, S: Selection<'g, J>>(&self, by: S) -> Result<GroupBy> {
         let selected_keys = self.select_series(by)?;
 
         let groups = match selected_keys.len() {
@@ -457,9 +457,9 @@ impl AggFirst for LargeListChunked {}
 impl<'df, 'selection_str> GroupBy<'df, 'selection_str> {
     /// Select the column by which the determine the groups.
     /// You can select a single column or a slice of columns.
-    pub fn select<S>(mut self, selection: S) -> Self
+    pub fn select<S, J>(mut self, selection: S) -> Self
     where
-        S: Selection<'selection_str>,
+        S: Selection<'selection_str, J>,
     {
         self.selected_agg = Some(selection.to_selection_vec());
         self

polars/src/frame/mod.rs

@@ -396,19 +396,19 @@ impl DataFrame {
     ///     }
     /// }
     /// ```
-    pub fn select<'a, S>(&self, selection: S) -> Result<Self>
+    pub fn select<'a, S, J>(&self, selection: S) -> Result<Self>
     where
-        S: Selection<'a>,
+        S: Selection<'a, J>,
     {
         let selected = self.select_series(selection)?;
         let df = DataFrame::new_no_checks(selected);
         Ok(df)
     }
 
     /// Select column(s) from this DataFrame and return them into a Vector.
-    pub fn select_series<'a, S>(&self, selection: S) -> Result<Vec<Series>>
+    pub fn select_series<'a, S, J>(&self, selection: S) -> Result<Vec<Series>>
     where
-        S: Selection<'a>,
+        S: Selection<'a, J>,
     {
         let cols = selection.to_selection_vec();
         let selected = cols

polars/src/frame/select.rs

@@ -1,52 +1,53 @@
-pub trait Selection<'a> {
+pub trait Selection<'a, S> {
     fn to_selection_vec(self) -> Vec<&'a str>;
 }
 
-impl<'a> Selection<'a> for &'a str {
+impl<'a> Selection<'a, &str> for &'a str {
     fn to_selection_vec(self) -> Vec<&'a str> {
         vec![self]
     }
 }
 
-impl<'a> Selection<'a> for Vec<&'a str> {
+impl<'a> Selection<'a, &str> for Vec<&'a str> {
     fn to_selection_vec(self) -> Vec<&'a str> {
         self
     }
 }
 
-impl<'a, T> Selection<'a> for &T
+impl<'a, T, S: 'a> Selection<'a, S> for &'a T
 where
-    T: AsRef<[&'a str]>,
+    T: AsRef<[S]>,
+    S: AsRef<str>,
 {
     fn to_selection_vec(self) -> Vec<&'a str> {
-        self.as_ref().iter().copied().collect()
+        self.as_ref().iter().map(|s| s.as_ref()).collect()
     }
 }
 
-impl<'a> Selection<'a> for (&'a str, &'a str) {
+impl<'a> Selection<'a, &str> for (&'a str, &'a str) {
     fn to_selection_vec(self) -> Vec<&'a str> {
         vec![self.0, self.1]
     }
 }
-impl<'a> Selection<'a> for (&'a str, &'a str, &'a str) {
+impl<'a> Selection<'a, &str> for (&'a str, &'a str, &'a str) {
     fn to_selection_vec(self) -> Vec<&'a str> {
         vec![self.0, self.1, self.2]
     }
 }
 
-impl<'a> Selection<'a> for (&'a str, &'a str, &'a str, &'a str) {
+impl<'a> Selection<'a, &str> for (&'a str, &'a str, &'a str, &'a str) {
     fn to_selection_vec(self) -> Vec<&'a str> {
         vec![self.0, self.1, self.2, self.3]
     }
 }
 
-impl<'a> Selection<'a> for (&'a str, &'a str, &'a str, &'a str, &'a str) {
+impl<'a> Selection<'a, &str> for (&'a str, &'a str, &'a str, &'a str, &'a str) {
     fn to_selection_vec(self) -> Vec<&'a str> {
         vec![self.0, self.1, self.2, self.3, self.4]
     }
 }
 
-impl<'a> Selection<'a> for (&'a str, &'a str, &'a str, &'a str, &'a str, &'a str) {
+impl<'a> Selection<'a, &str> for (&'a str, &'a str, &'a str, &'a str, &'a str, &'a str) {
     fn to_selection_vec(self) -> Vec<&'a str> {
         vec![self.0, self.1, self.2, self.3, self.4, self.5]
     }