Renaming the special methods of the formatters.

The IPython formatters use special methods to compute the format
of objects. These special methods have names like "__html__", but
with this commit these have been changed to "_repr_html_".

I have also added a Javascript formatter and fixed a bug in
pylab tools in getfigs.

docs/examples/core/display.py

@@ -0,0 +1,26 b''
+"""Code that shows off the IPython display logic.
+"""
+
+from IPython.core.display import (
+    display, display_pretty, display_html,
+    display_svg, display_json
+)
+
+class Circle(object):
+
+    def __init__(self, radius):
+        self.radius = radius
+
+    def _repr_pretty_(self, p, cycle):
+        p.text(u"\u25CB")
+
+    __pretty__ = _repr_pretty_
+
+    def _repr_html_(self):
+        return "<h1>Cirle: radius=%s</h1>" % self.radius
+
+    def _repr_svg_(self):
+        return """<svg>
+<circle cx="100" cy="50" r="40" stroke="black" stroke-width="2" fill="red"/>
+</svg>"""
+

IPython/core/display.py

@@ -119,4 +119,12 b' def display_json(*objs):'
     display(*objs, include=['text/plain','application/json'])
 
 
+def display_javascript(*objs):
+    """Display the Javascript representation of an object.
 
+    Parameters
+    ----------
+    objs : tuple of objects
+        The Python objects to display.
+    """
+    display(*objs, include=['text/plain','application/javascript'])

IPython/core/formatters.py

@@ -52,7 +52,8 b' class DisplayFormatter(Configurable):'
             SVGFormatter,
             PNGFormatter,
             LatexFormatter,
-            JSONFormatter
+            JSONFormatter,
+            JavascriptFormatter
         ]
         d = {}
         for cls in formatter_classes:
@@ -220,15 +221,14 b' class BaseFormatter(Configurable):'
             obj_id = id(obj)
             try:
                 obj_class = getattr(obj, '__class__', None) or type(obj)
-                if hasattr(obj_class, self.print_method):
-                    printer = getattr(obj_class, self.print_method)
-                    return printer(obj)
+                # First try to find registered singleton printers for the type.
                 try:
                     printer = self.singleton_printers[obj_id]
                 except (TypeError, KeyError):
                     pass
                 else:
                     return printer(obj)
+                # Next look for type_printers.
                 for cls in pretty._get_mro(obj_class):
                     if cls in self.type_printers:
                         return self.type_printers[cls](obj)
@@ -236,6 +236,10 b' class BaseFormatter(Configurable):'
                         printer = self._in_deferred_types(cls)
                         if printer is not None:
                             return printer(obj)
+                # Finally look for special method names.
+                if hasattr(obj_class, self.print_method):
+                    printer = getattr(obj_class, self.print_method)
+                    return printer(obj)
                 return None
             except Exception:
                 pass
@@ -442,66 +446,80 b' class HTMLFormatter(BaseFormatter):'
     """An HTML formatter.
 
     To define the callables that compute the HTML representation of your
-    objects, define a :meth:`__html__` method or use the :meth:`for_type`
+    objects, define a :meth:`_repr_html_` method or use the :meth:`for_type`
     or :meth:`for_type_by_name` methods to register functions that handle
     this.
     """
     format_type = Str('text/html')
 
-    print_method = Str('__html__')
+    print_method = Str('_repr_html_')
 
 
 class SVGFormatter(BaseFormatter):
     """An SVG formatter.
 
     To define the callables that compute the SVG representation of your
-    objects, define a :meth:`__svg__` method or use the :meth:`for_type`
+    objects, define a :meth:`_repr_svg_` method or use the :meth:`for_type`
     or :meth:`for_type_by_name` methods to register functions that handle
     this.
     """
     format_type = Str('image/svg+xml')
 
-    print_method = Str('__svg__')
+    print_method = Str('_repr_svg_')
 
 
 class PNGFormatter(BaseFormatter):
     """A PNG formatter.
 
     To define the callables that compute the PNG representation of your
-    objects, define a :meth:`__png__` method or use the :meth:`for_type`
+    objects, define a :meth:`_repr_png_` method or use the :meth:`for_type`
     or :meth:`for_type_by_name` methods to register functions that handle
-    this. The raw data should be the base64 encoded raw png data.
+    this.
+
+    The raw data should be the base64 encoded raw png data.
     """
     format_type = Str('image/png')
 
-    print_method = Str('__png__')
+    print_method = Str('_repr_png_')
 
 
 class LatexFormatter(BaseFormatter):
     """A LaTeX formatter.
 
     To define the callables that compute the LaTeX representation of your
-    objects, define a :meth:`__latex__` method or use the :meth:`for_type`
+    objects, define a :meth:`_repr_latex_` method or use the :meth:`for_type`
     or :meth:`for_type_by_name` methods to register functions that handle
     this.
     """
     format_type = Str('text/latex')
 
-    print_method = Str('__latex__')
+    print_method = Str('_repr_latex_')
 
 
 class JSONFormatter(BaseFormatter):
     """A JSON string formatter.
 
     To define the callables that compute the JSON string representation of
-    your objects, define a :meth:`__json__` method or use the :meth:`for_type`
+    your objects, define a :meth:`_repr_json_` method or use the :meth:`for_type`
     or :meth:`for_type_by_name` methods to register functions that handle
     this.
     """
     format_type = Str('application/json')
 
-    print_method = Str('__json__')
+    print_method = Str('_repr_json_')
+
+
+class JavascriptFormatter(BaseFormatter):
+    """A Javascript formatter.
+
+    To define the callables that compute the Javascript representation of
+    your objects, define a :meth:`_repr_javascript_` method or use the 
+    :meth:`for_type` or :meth:`for_type_by_name` methods to register functions
+    that handle this.
+    """
+    format_type = Str('application/javascript')
 
+    print_method = Str('_repr_javascript_')
 
 FormatterABC.register(BaseFormatter)
 FormatterABC.register(PlainTextFormatter)
@@ -510,6 +528,7 b' FormatterABC.register(SVGFormatter)'
 FormatterABC.register(PNGFormatter)
 FormatterABC.register(LatexFormatter)
 FormatterABC.register(JSONFormatter)
+FormatterABC.register(JavascriptFormatter)
 
 
 def format_display_data(obj, include=None, exclude=None):

IPython/core/usage.py

@@ -458,7 +458,7 b' Python objects can simply be passed to these functions and the appropriate'
 representations will be displayed in the console as long as the objects know
 how to compute those representations. The easiest way of teaching objects how
 to format themselves in various representations is to define special methods
-such as: ``__html``, ``__svg__`` and ``__png__``. IPython's display formatters
+such as: ``_repr_html_``, ``_repr_svg_`` and ``_repr_png_``. IPython's display formatters
 can also be given custom formatter functions for various types::
 
     In [6]: ip = get_ipython()

IPython/extensions/sympy_printing.py

@@ -39,7 +39,7 b' def print_basic_unicode(o, p, cycle):'
 
 
 def print_png(o):
-    """A funciton to display sympy expression using LaTex -> PNG."""
+    """A function to display sympy expression using LaTex -> PNG."""
     s = latex(o, mode='inline')
     # mathtext does not understand certain latex flags, so we try to replace
     # them with suitable subs.

IPython/lib/pylabtools.py

@@ -60,6 +60,7 b' def getfigs(*fig_nums):'
             f = Gcf.figs.get(num)
             if f is None:
                 print('Warning: figure %s not available.' % num)
+            else:
             figs.append(f.canvas.figure)
         return figs