Implement select_columns (#39)

datafusion/tests/test_dataframe.py

@@ -61,6 +61,16 @@ def test_select(df):
     assert result.column(1) == pa.array([-3, -3, -3])
 
 
+def test_select_colums(df):
+    df = df.select_columns("b", "a")
+
+    # execute and collect the first (and only) batch
+    result = df.collect()[0]
+
+    assert result.column(0) == pa.array([4, 5, 6])
+    assert result.column(1) == pa.array([1, 2, 3])
+
+
 def test_filter(df):
     df = df.select(
         column("a") + column("b"),

src/dataframe.rs

@@ -51,6 +51,12 @@ impl PyDataFrame {
         self.df.schema().into()
     }
 
+    #[args(args = "*")]
+    fn select_columns(&self, args: Vec<&str>) -> PyResult<Self> {
+        let df = self.df.select_columns(&args)?;
+        Ok(Self::new(df))
+    }
+
     #[args(args = "*")]
     fn select(&self, args: Vec<PyExpr>) -> PyResult<Self> {
         let expr = args.into_iter().map(|e| e.into()).collect();