diff --git a/python_ls/_ls.py b/python_ls/_ls.py
index d5fe516..2d17de3 100644
--- a/python_ls/_ls.py
+++ b/python_ls/_ls.py
@@ -21,16 +21,18 @@ def ls(obj, attr=None, depth=None, dunder=False, under=True):
     :param under: If True single underscore prefixed attributes are ignored, default is enabled
     :return: None
     """
-    if depth is None:
-        depth = 1
-
     for attr, value in iter_ls(obj, attr=attr, depth=depth,
                                dunder=dunder, under=under):
         size = ''
         if has_pandas and isinstance(value, pd.DataFrame):
             size = '{0}x{1}'.format(*value.shape)
         elif hasattr(value, '__len__'):
-            size = len(value)
+            try:
+                size = len(value)
+            except TypeError as exc:
+                # certain constructor object such as dict, list have a
+                # __len__ method but it throws a TypeError
+                pass
         type_name = type(value).__name__
         print('{:<60}{:>20}{:>7}'.format(attr, type_name, size))
 
diff --git a/tests/test_ls.py b/tests/test_ls.py
index 1a71368..b9ee357 100644
--- a/tests/test_ls.py
+++ b/tests/test_ls.py
@@ -1,4 +1,4 @@
-from python_ls import iter_ls
+from python_ls import iter_ls, ls
 import pytest
 
 
@@ -14,7 +14,8 @@ def test_obj():
     o.foo.bar.something = Object()
     o.foo.bar.aaa = Object()
     o.foo.bar.bbb = Object()
-    o.foo.bar._something_else = dict  # a callable (lambda recurses infinitely in Python 2.7 when depth=None)
+    o.foo.bar._something_else = lambda: None
+    o.foo.bar.constructor_obj = dict
     o.foo.baz = {'something_weird': 'going on', 'blah': 'bleh'}
     o.lala = Object()
     o.lala.lele = Object()
@@ -51,3 +52,29 @@ def test_depth_is_None(test_obj):
     actual = [x[0] for x in iter_ls(test_obj, 'something', depth=None)]
     assert actual == expected
 
+
+def test_iter_ls_constructor_obj(test_obj):
+    expected = ['foo.bar.constructor_obj()']
+
+    actual = [x[0] for x in iter_ls(test_obj, 'constructor', depth=None)]
+    assert actual == expected
+
+
+def test_basic_ls_usage(test_obj, capsys):
+    ls(test_obj, 'something')
+    out, err = capsys.readouterr()
+    expect = [
+        ['foo.bar._something_else()', 'function'],
+        ['foo.bar.something', 'Object'],
+        ["foo.baz['something_weird']", 'str', '8'],
+        ['lala.something', 'Object']
+    ]
+    assert expect == [line.split() for line in out.splitlines()]
+
+
+def test_ls_constructor_obj(test_obj, capsys):
+    ls(test_obj, 'constructor')
+    out, err = capsys.readouterr()
+    expect = [['foo.bar.constructor_obj()', 'type']]
+    assert expect == [line.split() for line in out.splitlines()]
+