BUG: Restore return value in notebook reprs (pandas-dev#16171)

* BUG: Restore return value in notebook reprs

Monkey patches the _ipython_display_ method onto NDFrame, so that
notebook cells have a real return value. Setting the
display.html.table_schema will monkey patch the method on,
and remove it when unset.

closes ipython/ipython#10491

* Define in generic.py

* PEP8

Author: TomAugspurger

pandas/core/config_init.py

@@ -340,6 +340,21 @@ def mpl_style_cb(key):
     return val
 
 
+def table_schema_cb(key):
+    # Having _ipython_display_ defined messes with the return value
+    # from cells, so the Out[x] dictionary breaks.
+    # Currently table schema is the only thing using it, so we'll
+    # monkey patch `_ipython_display_` onto NDFrame when config option
+    # is set
+    # see https://github.com/pandas-dev/pandas/issues/16168
+    from pandas.core.generic import NDFrame, _ipython_display_
+
+    if cf.get_option(key):
+        NDFrame._ipython_display_ = _ipython_display_
+    elif getattr(NDFrame, '_ipython_display_', None):
+        del NDFrame._ipython_display_
+
+
 with cf.config_prefix('display'):
     cf.register_option('precision', 6, pc_precision_doc, validator=is_int)
     cf.register_option('float_format', None, float_format_doc,
@@ -407,7 +422,7 @@ def mpl_style_cb(key):
     cf.register_option('latex.multirow', False, pc_latex_multirow,
                        validator=is_bool)
     cf.register_option('html.table_schema', False, pc_table_schema_doc,
-                       validator=is_bool)
+                       validator=is_bool, cb=table_schema_cb)
 
 
 cf.deprecate_option('display.line_width',

pandas/core/generic.py

@@ -130,31 +130,6 @@ def __init__(self, data, axes=None, copy=False, dtype=None,
         object.__setattr__(self, '_data', data)
         object.__setattr__(self, '_item_cache', {})
 
-    def _ipython_display_(self):
-        try:
-            from IPython.display import display
-        except ImportError:
-            return None
-
-        # Series doesn't define _repr_html_ or _repr_latex_
-        latex = self._repr_latex_() if hasattr(self, '_repr_latex_') else None
-        html = self._repr_html_() if hasattr(self, '_repr_html_') else None
-        try:
-            table_schema = self._repr_table_schema_()
-        except Exception as e:
-            warnings.warn("Cannot create table schema representation. "
-                          "{}".format(e), UnserializableWarning)
-            table_schema = None
-        # We need the inital newline since we aren't going through the
-        # usual __repr__. See
-        # https://github.com/pandas-dev/pandas/pull/14904#issuecomment-277829277
-        text = "\n" + repr(self)
-
-        reprs = {"text/plain": text, "text/html": html, "text/latex": latex,
-                 "application/vnd.dataresource+json": table_schema}
-        reprs = {k: v for k, v in reprs.items() if v}
-        display(reprs, raw=True)
-
     def _repr_table_schema_(self):
         """
         Not a real Jupyter special repr method, but we use the same
@@ -6283,6 +6258,38 @@ def logical_func(self, axis=None, bool_only=None, skipna=None, level=None,
     return set_function_name(logical_func, name, cls)
 
 
+def _ipython_display_(self):
+    # Having _ipython_display_ defined messes with the return value
+    # from cells, so the Out[x] dictionary breaks.
+    # Currently table schema is the only thing using it, so we'll
+    # monkey patch `_ipython_display_` onto NDFrame when config option
+    # is set
+    # see https://github.com/pandas-dev/pandas/issues/16168
+    try:
+        from IPython.display import display
+    except ImportError:
+        return None
+
+    # Series doesn't define _repr_html_ or _repr_latex_
+    latex = self._repr_latex_() if hasattr(self, '_repr_latex_') else None
+    html = self._repr_html_() if hasattr(self, '_repr_html_') else None
+    try:
+        table_schema = self._repr_table_schema_()
+    except Exception as e:
+        warnings.warn("Cannot create table schema representation. "
+                      "{}".format(e), UnserializableWarning)
+        table_schema = None
+    # We need the inital newline since we aren't going through the
+    # usual __repr__. See
+    # https://github.com/pandas-dev/pandas/pull/14904#issuecomment-277829277
+    text = "\n" + repr(self)
+
+    reprs = {"text/plain": text, "text/html": html, "text/latex": latex,
+             "application/vnd.dataresource+json": table_schema}
+    reprs = {k: v for k, v in reprs.items() if v}
+    display(reprs, raw=True)
+
+
 # install the indexes
 for _name, _indexer in indexing.get_indexers_list():
     NDFrame._create_indexer(_name, _indexer)

pandas/tests/io/formats/test_printing.py

@@ -203,6 +203,33 @@ def test_config_default_off(self):
 
         assert result is None
 
+    def test_config_monkeypatches(self):
+        # GH 10491
+        df = pd.DataFrame({"A": [1, 2]})
+        assert not hasattr(df, '_ipython_display_')
+        assert not hasattr(df['A'], '_ipython_display_')
+
+        with pd.option_context('display.html.table_schema', True):
+            assert hasattr(df, '_ipython_display_')
+            # smoke test that it works
+            df._ipython_display_()
+            assert hasattr(df['A'], '_ipython_display_')
+            df['A']._ipython_display_()
+
+        assert not hasattr(df, '_ipython_display_')
+        assert not hasattr(df['A'], '_ipython_display_')
+        # re-unsetting is OK
+        assert not hasattr(df, '_ipython_display_')
+        assert not hasattr(df['A'], '_ipython_display_')
+
+        # able to re-set
+        with pd.option_context('display.html.table_schema', True):
+            assert hasattr(df, '_ipython_display_')
+            # smoke test that it works
+            df._ipython_display_()
+            assert hasattr(df['A'], '_ipython_display_')
+            df['A']._ipython_display_()
+
 
 # TODO: fix this broken test