Add a types.MappingProxyType pretty printer #9821

Also fixed the _dict_pprinter_factory indentation step

IPython/lib/pretty.py

@@ -605,7 +605,8 b' def _dict_pprinter_factory(start, end, basetype=None):'
 
         if cycle:
             return p.text('{...}')
-        p.begin_group(1, start)
+        step = len(start)
+        p.begin_group(step, start)
         keys = obj.keys()
         # if dict isn't large enough to be truncated, sort keys before displaying
         if not (p.max_seq_length and len(obj) >= p.max_seq_length):
@@ -621,7 +622,7 b' def _dict_pprinter_factory(start, end, basetype=None):'
             p.pretty(key)
             p.text(': ')
             p.pretty(obj[key])
-        p.end_group(1, end)
+        p.end_group(step, end)
     return inner
 
 
@@ -760,6 +761,8 b' try:'
     _type_pprinters[types.ClassType] = _type_pprint
     _type_pprinters[types.SliceType] = _repr_pprint
 except AttributeError: # Python 3
+    _type_pprinters[types.MappingProxyType] = \
+        _dict_pprinter_factory('mappingproxy({', '})')
     _type_pprinters[slice] = _repr_pprint
     
 try:

IPython/lib/tests/test_pretty.py

@@ -7,11 +7,12 b''
 from __future__ import print_function
 
 from collections import Counter, defaultdict, deque, OrderedDict
+import types, string
 
 import nose.tools as nt
 
 from IPython.lib import pretty
-from IPython.testing.decorators import skip_without, py2_only
+from IPython.testing.decorators import skip_without, py2_only, py3_only
 from IPython.utils.py3compat import PY3, unicode_to_str
 
 if PY3:
@@ -436,3 +437,48 b' def test_collections_counter():'
     ]
     for obj, expected in cases:
         nt.assert_equal(pretty.pretty(obj), expected)
+
+@py3_only
+def test_mappingproxy():
+    MP = types.MappingProxyType
+    underlying_dict = {}
+    mp_recursive = MP(underlying_dict)
+    underlying_dict[2] = mp_recursive
+    underlying_dict[3] = underlying_dict
+
+    cases = [
+        (MP({}), "mappingproxy({})"),
+        (MP({None: MP({})}), "mappingproxy({None: mappingproxy({})})"),
+        (MP({k: k.upper() for k in string.ascii_lowercase}),
+         "mappingproxy({'a': 'A',\n"
+         "              'b': 'B',\n"
+         "              'c': 'C',\n"
+         "              'd': 'D',\n"
+         "              'e': 'E',\n"
+         "              'f': 'F',\n"
+         "              'g': 'G',\n"
+         "              'h': 'H',\n"
+         "              'i': 'I',\n"
+         "              'j': 'J',\n"
+         "              'k': 'K',\n"
+         "              'l': 'L',\n"
+         "              'm': 'M',\n"
+         "              'n': 'N',\n"
+         "              'o': 'O',\n"
+         "              'p': 'P',\n"
+         "              'q': 'Q',\n"
+         "              'r': 'R',\n"
+         "              's': 'S',\n"
+         "              't': 'T',\n"
+         "              'u': 'U',\n"
+         "              'v': 'V',\n"
+         "              'w': 'W',\n"
+         "              'x': 'X',\n"
+         "              'y': 'Y',\n"
+         "              'z': 'Z'})"),
+        (mp_recursive, "mappingproxy({2: {...}, 3: {2: {...}, 3: {...}}})"),
+        (underlying_dict,
+         "{2: mappingproxy({2: {...}, 3: {...}}), 3: {...}}"),
+    ]
+    for obj, expected in cases:
+        nt.assert_equal(pretty.pretty(obj), expected)