From 5692bbc821f02d15003e24d421de71c2e0a622d7 Mon Sep 17 00:00:00 2001
From: Ritchie Vink <ritchie46@gmail.com>
Date: Mon, 19 Jul 2021 10:34:19 +0200
Subject: [PATCH] python: allow empty series creation

---
 py-polars/polars/eager/series.py |  5 ++++-
 py-polars/tests/test_series.py   | 13 +++++++++----
 2 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/py-polars/polars/eager/series.py b/py-polars/polars/eager/series.py
index 615e0fb625ad..b04e5a1543f8 100644
--- a/py-polars/polars/eager/series.py
+++ b/py-polars/polars/eager/series.py
@@ -144,8 +144,11 @@ def __init__(
             raise ValueError(
                 f"Constructing a Series with a dict is not supported for {values}"
             )
+        elif values is None and dtype is None:
+            dtype = Float32
+            values = []
         elif values is None:
-            raise ValueError("Series values cannot be None.")
+            values = []
 
         # castable to numpy
         if not isinstance(values, np.ndarray) and not nullable:
diff --git a/py-polars/tests/test_series.py b/py-polars/tests/test_series.py
index b64ce31a777c..c0041e6cb929 100644
--- a/py-polars/tests/test_series.py
+++ b/py-polars/tests/test_series.py
@@ -21,12 +21,10 @@ def test_init_inputs():
 
     pl.Series([1, 2])
     pl.Series(values=[1, 2])
+    pl.Series()
+    pl.Series("a")
 
     # Bad inputs
-    with pytest.raises(ValueError):
-        pl.Series()
-    with pytest.raises(ValueError):
-        pl.Series("a")
     with pytest.raises(ValueError):
         pl.Series([1, 2, 3], [1, 2, 3])
     with pytest.raises(ValueError):
@@ -318,6 +316,13 @@ def test_iter():
     assert sum(s) == 6
 
 
+def test_empty():
+    a = pl.Series(dtype=pl.Int8)
+    assert a.dtype == pl.Int8
+    a = pl.Series()
+    assert a.dtype == pl.Float32
+
+
 def test_describe():
     num_s = pl.Series([1, 2, 3])
     float_s = pl.Series([1.3, 4.6, 8.9])