maintain instances of exporters for use in export_by_name

avoids recreating new Exporters every time

IPython/nbconvert/exporters/export.py

@@ -1,211 +1,214 b''
 """
 Module containing single call export functions.
 """
 #-----------------------------------------------------------------------------
 # Copyright (c) 2013, the IPython Development Team.
 #
 # Distributed under the terms of the Modified BSD License.
 #
 # The full license is in the file COPYING.txt, distributed with this software.
 #-----------------------------------------------------------------------------
 
 #-----------------------------------------------------------------------------
 # Imports
 #-----------------------------------------------------------------------------
 
 from functools import wraps
 
 from IPython.nbformat.v3.nbbase import NotebookNode
 from IPython.config import Config
 
 from .exporter import Exporter
 from .html import HTMLExporter
 from .slides import SlidesExporter
 from .latex import LatexExporter
 from .markdown import MarkdownExporter
 from .python import PythonExporter
 from .rst import RSTExporter
 
 #-----------------------------------------------------------------------------
 # Classes
 #-----------------------------------------------------------------------------
 
 def DocDecorator(f):
     
     #Set docstring of function
     f.__doc__ = f.__doc__ + """
     nb : Notebook node
     config : config (optional, keyword arg)
         User configuration instance.
     resources : dict (optional, keyword arg)
         Resources used in the conversion process.
         
     Returns
     ----------
     tuple- output, resources, exporter_instance
     output : str
         Jinja 2 output.  This is the resulting converted notebook.
     resources : dictionary
         Dictionary of resources used prior to and during the conversion 
         process.
     exporter_instance : Exporter
         Instance of the Exporter class used to export the document.  Useful
         to caller because it provides a 'file_extension' property which
         specifies what extension the output should be saved as.
 
     WARNING: API WILL CHANGE IN FUTURE RELEASES OF NBCONVERT
     """
             
     @wraps(f)
     def decorator(*args, **kwargs):
         return f(*args, **kwargs)
     
     return decorator
 
 
 #-----------------------------------------------------------------------------
 # Functions
 #-----------------------------------------------------------------------------
 
 __all__ = [
     'export',
     'export_html',
     'export_custom',
     'export_slides',
     'export_latex',
     'export_markdown',
     'export_python',
     'export_rst',
     'export_by_name',
     'get_export_names',
     'ExporterNameError'
 ]
 
 
 class ExporterNameError(NameError):
     pass
 
+_exporters = {}
 
 @DocDecorator
 def export(exporter, nb, **kw):
     """
     Export a notebook object using specific exporter class.
     
     exporter : Exporter class type or instance
         Class type or instance of the exporter that should be used.  If the 
         method initializes it's own instance of the class, it is ASSUMED that 
         the class type provided exposes a constructor (__init__) with the same 
         signature as the base Exporter class.
     """
     
     #Check arguments
     if exporter is None:
         raise TypeError("Exporter is None")
     elif not isinstance(exporter, Exporter) and not issubclass(exporter, Exporter):
         raise TypeError("exporter does not inherit from Exporter (base)")
     if nb is None:
         raise TypeError("nb is None")
     
     #Create the exporter
     resources = kw.pop('resources', None)
     if isinstance(exporter, Exporter):
         exporter_instance = exporter
     else:
-        exporter_instance = exporter(**kw)
+        if exporter not in _exporters:
+            _exporters[exporter] = exporter(**kw)
+        exporter_instance = _exporters[exporter]
 
     #Try to convert the notebook using the appropriate conversion function.
     if isinstance(nb, NotebookNode):
         output, resources = exporter_instance.from_notebook_node(nb, resources)
     elif isinstance(nb, basestring):
         output, resources = exporter_instance.from_filename(nb, resources)
     else:
         output, resources = exporter_instance.from_file(nb, resources)
     return output, resources
 
 
 @DocDecorator
 def export_custom(nb, **kw):
     """
     Export a notebook object to a custom format
     """
     return export(Exporter, nb, **kw)
 
 
 @DocDecorator
 def export_html(nb, **kw):
     """
     Export a notebook object to HTML
     """
     return export(HTMLExporter, nb, **kw)
 
 
 @DocDecorator
 def export_slides(nb, **kw):
     """
     Export a notebook object to Slides
     """
     return export(SlidesExporter, nb, **kw)
 
 
 @DocDecorator
 def export_latex(nb, **kw):
     """
     Export a notebook object to LaTeX
     """
     return export(LatexExporter, nb, **kw)
 
 
 @DocDecorator
 def export_markdown(nb, **kw):
     """
     Export a notebook object to Markdown
     """
     return export(MarkdownExporter, nb, **kw)
 
 
 @DocDecorator
 def export_python(nb, **kw):
     """
     Export a notebook object to Python
     """
     return export(PythonExporter, nb, **kw)
 
 
 @DocDecorator
 def export_rst(nb, **kw):
     """
     Export a notebook object to reStructuredText
     """
     return export(RSTExporter, nb, **kw)
 
 
 @DocDecorator
 def export_by_name(format_name, nb, **kw):
     """
     Export a notebook object to a template type by its name.  Reflection
     (Inspect) is used to find the template's corresponding explicit export
     method defined in this module.  That method is then called directly.
     
     format_name : str
         Name of the template style to export to.
     """
     
     function_name = "export_" + format_name.lower()
     
     if function_name in globals():
         return globals()[function_name](nb, **kw)
     else:
         raise ExporterNameError("template for `%s` not found" % function_name)
 
 
 def get_export_names():
     """Return a list of the currently supported export targets
 
     WARNING: API WILL CHANGE IN FUTURE RELEASES OF NBCONVERT"""
     
     # grab everything after 'export_'
     l = [x[len('export_'):] for x in __all__ if x.startswith('export_')]
     
     # filter out the one method that is not a template
     l = [x for x in l if 'by_name' not in x]
     return sorted(l)