Import hooks to set up inline backend when matplotlib is loaded

ipykernel/kernelapp.py

@@ -362,6 +362,15 @@ def init_extensions(self):
                 self.log.debug('ipywidgets package not installed.  Widgets will not be available.')
         # END HARDCODED WIDGETS HACK
 
+    mpl_plots_inline = Bool(True, config=True,
+        help="Make matplotlib send plots to Jupyter frontends by default."
+    )
+
+    def init_mpl_shim(self):
+        if self.mpl_plots_inline:
+            from . import mplshim
+            mplshim.install_import_hook()
+
     @catch_config_error
     def initialize(self, argv=None):
         super(IPKernelApp, self).initialize(argv)
@@ -387,6 +396,7 @@ def initialize(self, argv=None):
             self.init_gui_pylab()
             self.init_extensions()
             self.init_code()
+            self.init_mpl_shim()
         # flush stdout/stderr, so that anything written to these streams during
         # initialization do not get associated with the first execution request
         sys.stdout.flush()

ipykernel/mplshim.py

@@ -0,0 +1,89 @@
+"""Import hooks to activate our inline backend when matplotlib is loaded
+"""
+
+import imp
+import sys
+
+def set_inline_backend(mpl):
+    from IPython.core.pylabtools import backends, configure_inline_support
+    from .kernelapp import IPKernelApp
+    mpl.interactive(True)
+    mpl.use(backends['inline'])
+    configure_inline_support(IPKernelApp.instance().shell, backends['inline'])
+
+class Py2MPLFinderShim(object):
+    @classmethod
+    def find_module(cls, fullname, path=None):
+        if (fullname != 'matplotlib') or (path is not None):
+            return None
+
+        try:
+            res = imp.find_module('matplotlib')
+        except ImportError:
+            return None
+        else:
+            return Py2MPLLoaderShim(*res)
+
+class Py2MPLLoaderShim(object):
+    def __init__(self, file, pathname, description):
+        self.file = file
+        self.pathname = pathname
+        self.description = description
+
+    def load_module(self, fullname):
+        # fullname should only ever be 'matplotlib' here
+        m = imp.load_module(fullname, self.file, self.pathname, self.description)
+        set_inline_backend(m)
+        return m
+
+try:
+    from importlib.machinery import PathFinder
+except ImportError:
+    # Python 2
+    finder_shim = Py2MPLFinderShim
+else:
+    class Py3MPLFinderShim(PathFinder):
+        # On Python 3.4 and above, find_spec() will be called
+        @classmethod
+        def find_spec(cls, fullname, path=None, target=None):
+            if (fullname != 'matplotlib') or (path is not None):
+                return None
+
+            spec = PathFinder.find_spec(fullname, path=None)
+            if spec is None:
+                return None
+
+            if spec.loader is not None:
+                spec.loader = Py3MPLLoaderShim(spec.loader)
+            return spec
+
+        # On Python 3.3 or below, find_module() will be called
+        @classmethod
+        def find_module(cls, fullname, path=None):
+            print(fullname, path)
+            if (fullname != 'matplotlib') or (path is not None):
+                return None
+
+            real_loader = PathFinder.find_module(fullname, path=None)
+            if real_loader is None:
+                return None
+            return Py3MPLLoaderShim(real_loader)
+
+    class Py3MPLLoaderShim(object):
+        def __init__(self, real_loader):
+            self.real_loader = real_loader
+
+        def load_module(self, fullname):
+            # fullname should only ever be 'matplotlib' here)
+            m = self.real_loader.load_module(fullname)
+            set_inline_backend(m)
+            return m
+
+
+    finder_shim = Py3MPLFinderShim
+
+def install_import_hook():
+    sys.meta_path.insert(0, finder_shim)
+
+def remove_import_hook():
+    sys.meta_path.remove(finder_shim)