Implement a human-readable str/repr for State objects

CHANGES.md

@@ -52,6 +52,8 @@ v0.15.0 (unreleased)
   and ``glue.viewers.common.qt.toolbar_mode`` to ``glue.viewers.matplotlib.toolbar_mode``
   and ``glue.viewers.matplotlib.qt.toolbar_mode``. [#1984]
 
+* Implement a human-readable str/repr for State objects. [#2021]
+
 * Avoiding importing Qt when using the base histogram and profile layer artists.
   [#2012]
 

glue/core/state_objects.py

@@ -1,5 +1,11 @@
 from __future__ import absolute_import, division, print_function
 
+try:
+    from textwrap import indent
+except ImportError:  # PY2
+    def indent(text, prefix):
+        return ''.join([prefix + line for line in text.splitlines(True)])
+
 from collections import defaultdict
 
 import numpy as np
@@ -81,6 +87,20 @@ def as_dict(self):
                 properties[name] = getattr(self, name)
         return properties
 
+    def __str__(self):
+        s = ""
+        state_dict = self.as_dict()
+        for key in sorted(state_dict):
+            value = state_dict[key]
+            if np.isscalar(value):
+                s += "{0}: {1}\n".format(key, value)
+            else:
+                s += "{0}: {1}\n".format(key, repr(value))
+        return s.strip()
+
+    def __repr__(self):
+        return "<{0}\n{1}\n>".format(self.__class__.__name__, indent(str(self), '  '))
+
     def __gluestate__(self, context):
         return {'values': dict((key, context.id(value)) for key, value in self.as_dict().items())}
 

glue/core/tests/test_state_objects.py

@@ -48,6 +48,38 @@ def test_state_serialization():
     assert state2.nested[2].nested == []
 
 
+EXPECTED_STR = """
+a: 2
+b: hello
+flat: <CallbackList with 3 elements>
+nested: <CallbackList with 3 elements>
+"""
+
+EXPECTED_REPR = """
+<SimpleTestState
+  a: 2
+  b: hello
+  flat: <CallbackList with 3 elements>
+  nested: <CallbackList with 3 elements>
+>
+"""
+
+
+def test_state_str_repr():
+
+    state1 = SimpleTestState()
+    state1.a = 2
+    state1.b = 'hello'
+    state1.flat = [1, 3, 4]
+
+    sub_state = SimpleTestState()
+
+    state1.nested = [1, 3, sub_state]
+
+    assert str(state1) == EXPECTED_STR.strip()
+    assert repr(state1) == EXPECTED_REPR.strip()
+
+
 class TestStateAttributeLimitsHelper():
 
     def setup_method(self, method):

glue/external/echo/list.py

@@ -15,6 +15,9 @@ def __init__(self, callback, *args, **kwargs):
         super(CallbackList, self).__init__(*args, **kwargs)
         self.callback = callback
 
+    def __repr__(self):
+        return "<CallbackList with {0} elements>".format(len(self))
+
     def append(self, value):
         super(CallbackList, self).append(value)
         if isinstance(value, HasCallbackProperties):