python to_json, run if no arg is given

pola-rs · Sep 12, 2021 · cacd13e · cacd13e
1 parent 677d69b
commit cacd13e
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diff --git a/py-polars/polars/eager/frame.py b/py-polars/polars/eager/frame.py
@@ -714,7 +714,7 @@ def to_json(
         to_string
             Ignore file argument and return a string.
         """
-        if to_string:
+        if to_string or file is None:
             file = BytesIO()
             self._df.to_json(file, pretty)
             file.seek(0)

diff --git a/py-polars/tests/test_io.py b/py-polars/tests/test_io.py
@@ -206,3 +206,11 @@ def test_copy():
     a = pl.Series("a", [1, 2])
     copy.copy(a).series_equal(a, True)
     copy.deepcopy(a).series_equal(a, True)
+
+
+def test_to_json():
+    # tests if it runs if no arg given
+    df = pl.DataFrame({"a": [1, 2, 3]})
+    assert (
+        df.to_json() == '{"columns":[{"name":"a","datatype":"Int64","values":[1,2,3]}]}'
+    )