Add welcome_message option to enable_pylab

This way, custom apps that enable pylab won't see it by default.  See for
example sympy/sympy#1489.

IPython/core/interactiveshell.py

@@ -2787,7 +2787,7 b' class InteractiveShell(SingletonConfigurable):'
     def enable_gui(self, gui=None):
         raise NotImplementedError('Implement enable_gui in a subclass')
 
-    def enable_pylab(self, gui=None, import_all=True):
+    def enable_pylab(self, gui=None, import_all=True, welcome_message=False):
         """Activate pylab support at runtime.
 
         This turns on support for matplotlib, preloads into the interactive
@@ -2814,7 +2814,7 b' class InteractiveShell(SingletonConfigurable):'
         # user_ns_hidden with this information.
         ns = {}
         try:
-            gui = pylab_activate(ns, gui, import_all, self)
+            gui = pylab_activate(ns, gui, import_all, self, welcome_message=welcome_message)
         except KeyError:
             error("Backend %r not supported" % gui)
             return

IPython/core/magics/pylab.py

@@ -85,4 +85,4 b' class PylabMagics(Magics):'
         else:
             import_all_status = True
 
-        self.shell.enable_pylab(parameter_s, import_all=import_all_status)
+        self.shell.enable_pylab(parameter_s, import_all=import_all_status, welcome_message=True)

IPython/core/pylabtools.py

@@ -319,7 +319,7 b' def configure_inline_support(shell, backend, user_ns=None):'
     user_ns['getfigs'] = getfigs
 
 
-def pylab_activate(user_ns, gui=None, import_all=True, shell=None):
+def pylab_activate(user_ns, gui=None, import_all=True, shell=None, welcome_message=False):
     """Activate pylab mode in the user's namespace.
 
     Loads and initializes numpy, matplotlib and friends for interactive use.
@@ -335,6 +335,10 b' def pylab_activate(user_ns, gui=None, import_all=True, shell=None):'
     import_all : optional, boolean
       If true, an 'import *' is done from numpy and pylab.
 
+    welcome_message : optional, boolean
+      If true, print a welcome message about pylab, which includes the backend
+      being used.
+
     Returns
     -------
     The actual gui used (if not given as input, it was obtained from matplotlib
@@ -356,12 +360,11 b' def pylab_activate(user_ns, gui=None, import_all=True, shell=None):'
     import_pylab(user_ns, import_all)
     if shell is not None:
         configure_inline_support(shell, backend, user_ns)
-        
-    print """
+    if welcome_message:
+        print """
 Welcome to pylab, a matplotlib-based Python environment [backend: %s].
 For more information, type 'help(pylab)'.""" % backend
-    # flush stdout, just to be safe
-    sys.stdout.flush()
-    
-    return gui
+        # flush stdout, just to be safe
+        sys.stdout.flush()
 
+    return gui

IPython/core/shellapp.py

@@ -197,7 +197,7 b' class InteractiveShellApp(Configurable):'
                     gui, backend = pylabtools.find_gui_and_backend(self.pylab)
                     self.log.info("Enabling GUI event loop integration, "
                               "toolkit=%s, pylab=%s" % (gui, self.pylab))
-                    shell.enable_pylab(gui, import_all=self.pylab_import_all)
+                    shell.enable_pylab(gui, import_all=self.pylab_import_all, welcome_message=True)
                 else:
                     self.log.info("Enabling GUI event loop integration, "
                                   "toolkit=%s" % self.gui)