Python expr dt namespace:

Add epoch_days, epoch_seconds and epoch_milliseconds

py-polars/docs/source/reference/expression.rst

@@ -250,6 +250,9 @@ The following methods are available under the `expr.dt` attribute.
     ExprDateTimeNameSpace.to_python_datetime
     ExprDateTimeNameSpace.timestamp
     ExprDateTimeNameSpace.buckets
+    ExprDateTimeNameSpace.epoch_days
+    ExprDateTimeNameSpace.epoch_milliseconds
+    ExprDateTimeNameSpace.epoch_seconds
 
 Strings
 -------

py-polars/polars/internals/expr.py

@@ -18,6 +18,7 @@
     Date,
     Datetime,
     Float64,
+    Int32,
     Object,
     UInt32,
     py_type_to_dtype,
@@ -2644,8 +2645,41 @@ def to_python_datetime(self) -> Expr:
             lambda s: s.dt.to_python_datetime(), return_dtype=Object
         )
 
+    def epoch_days(self) -> Expr:
+        """
+        Get the number of days since the unix EPOCH.
+        If the date is before the unix EPOCH, the number of days will be negative.
+
+        Returns
+        -------
+        Days as Int32
+        """
+        return wrap_expr(self._pyexpr).cast(Date).cast(Int32)
+
+    def epoch_milliseconds(self) -> Expr:
+        """
+        Get the number of milliseconds since the unix EPOCH
+        If the date is before the unix EPOCH, the number of milliseconds will be negative.
+
+        Returns
+        -------
+        Milliseconds as Int64
+        """
+        return self.timestamp()
+
+    def epoch_seconds(self) -> Expr:
+        """
+        Get the number of seconds since the unix EPOCH
+        If the date is before the unix EPOCH, the number of seconds will be negative.
+
+        Returns
+        -------
+        Milliseconds as Int64
+        """
+        return wrap_expr(self._pyexpr.dt_epoch_seconds())
+
     def timestamp(self) -> Expr:
-        """Return timestamp in ms as Int64 type."""
+        """Return timestamp in milliseconds as Int64 type."""
         return wrap_expr(self._pyexpr.timestamp())
 
 

py-polars/src/lazy/dsl.rs

@@ -529,6 +529,15 @@ impl PyExpr {
             )
             .into()
     }
+    pub fn dt_epoch_seconds(&self) -> PyExpr {
+        self.clone()
+            .inner
+            .map(
+                |s| s.timestamp().map(|ca| (ca / 1000).into_series()),
+                GetOutput::from_type(DataType::Int64),
+            )
+            .into()
+    }
 
     pub fn rolling_apply(&self, py: Python, window_size: usize, lambda: PyObject) -> PyExpr {
         // get the pypolars module