FIX: `to_table` failed on lists

Summary

Fix for #117 (closed)

Focus

• Performance
• Sufficient test

Test Environment

Run the unit test:

pytest --pdb --pdbcls=IPython.terminal.debugger:TerminalPdb unittests/test_table_converter.py::TableTest::test_list

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unittests/test_table_converter.py

@@ -27,6 +27,7 @@ from tempfile import NamedTemporaryFile
 import caosdb as db
 import pandas as pd
 from caosdb.apiutils import compare_entities
+from numpy import nan
 
 from caosadvancedtools.table_converter import (from_table, from_tsv, to_table,
                                                to_tsv)
@@ -42,7 +43,8 @@ class TableTest(unittest.TestCase):
 
     def test_empty(self):
         c = db.Container()
-        self.assertRaises(ValueError, to_table, c)
+        df = to_table(c)
+        assert df.shape == (0, 0)
 
     def test_different_props(self):
         r1 = db.Record()
@@ -65,6 +67,36 @@ class TableTest(unittest.TestCase):
         c.extend([r1, r2])
         self.assertRaises(ValueError, to_table, c)
 
+    def test_list(self):
+        r1 = db.Record()
+        r1.add_parent("no1")
+        r1.add_property("p1", value=1)
+        r1.add_property("p3", value=23)
+        r1.add_property("p4", value=[1])
+        r2 = db.Record()
+        r2.add_parent("no1")
+        r2.add_property("p1")
+        r2.add_property("p2", value=[20, 21])
+        r2.add_property("p3", value=[30, 31])
+        r2.add_property("p4", value=[40.0, 41.0])
+        r3 = db.Record()
+        r3.add_parent("no1")
+        r3.add_property("p5", value=[50, 51])
+        c = db.Container()
+        c.extend([r1, r2, r3])
+        result = to_table(c)
+        # NaN is hard to compare, so we replace it by -999
+        # autopep8: off
+        assert result.replace(to_replace=nan, value=-999).to_dict() == {
+            'p1': {0: 1,    1: -999,         2: -999},  # noqa: E202
+            'p3': {0: 23,   1: [30, 31],     2: -999},  # noqa: E202
+            'p4': {0: [1],  1: [40.0, 41.0], 2: -999},  # noqa: E202
+            'p2': {0: -999, 1: [20, 21],     2: -999},  # noqa: E202
+            'p5': {0: -999, 1: -999,         2: [50, 51]}
+        }
+        # autopep8: on
+        assert list(result.dtypes) == [float, object, object, object, object]
+
 
 class FromTsvTest(unittest.TestCase):
     def test_basic(self):