PRF: only try IPython if it is already imported

tacaswell · tacaswell · commit bc20fe246531 · 2015-09-08T21:37:46.000-04:00
This prevents importing IPython if it is not already imported. closes #5037
diff --git a/lib/matplotlib/pyplot.py b/lib/matplotlib/pyplot.py
@@ -112,6 +112,7 @@ def _backend_selection():
 _IP_REGISTERED = None
 _INSTALL_FIG_OBSERVER = False
 
+
 def install_repl_displayhook():
     """
     Install a repl display hook so that any stale figure are automatically
@@ -128,27 +129,30 @@ class _NotIPython(Exception):
     # see if we have IPython hooks around, if use them
 
     try:
-        from IPython import get_ipython
-        ip = get_ipython()
-        if ip is None:
-            raise _NotIPython()
-
-        if _IP_REGISTERED:
-            return
-
-        def post_execute():
-            if matplotlib.is_interactive():
-                draw_all()
-
-        # IPython >= 2
-        try:
-            ip.events.register('post_execute', post_execute)
-        except AttributeError:
-            # IPython 1.x
-            ip.register_post_execute(post_execute)
-
-        _IP_REGISTERED = post_execute
-        _INSTALL_FIG_OBSERVER = False
+        if 'IPython' in sys.modules:
+            from IPython import get_ipython
+            ip = get_ipython()
+            if ip is None:
+                raise _NotIPython()
+
+            if _IP_REGISTERED:
+                return
+
+            def post_execute():
+                if matplotlib.is_interactive():
+                    draw_all()
+
+            # IPython >= 2
+            try:
+                ip.events.register('post_execute', post_execute)
+            except AttributeError:
+                # IPython 1.x
+                ip.register_post_execute(post_execute)
+
+            _IP_REGISTERED = post_execute
+            _INSTALL_FIG_OBSERVER = False
+        else:
+            _INSTALL_FIG_OBSERVER = True
 
     # import failed or ipython is not running
     except (ImportError, _NotIPython):
