embed_kernel: only import zmq when needed

IPython/__init__.py

@@ -44,11 +44,6 b' from .config.loader import Config'
 from .core import release
 from .core.application import Application
 from .frontend.terminal.embed import embed
-try:
-    from .zmq.ipkernel import embed_kernel
-except ImportError:
-    def embed_kernel(*args, **kwargs):
-        raise ImportError("IPython.embed_kernel requires pyzmq >= 2.1.4")
 
 from .core.error import TryNext
 from .core.interactiveshell import InteractiveShell
@@ -61,3 +56,21 b' for author, email in release.authors.itervalues():'
     __author__ += author + ' <' + email + '>\n'
 __license__  = release.license
 __version__  = release.version
+
+def caller_module_and_locals():
+    """Returns (module, locals) of the caller"""
+    caller = sys._getframe(2)
+    global_ns = caller.f_globals
+    module = sys.modules[global_ns['__name__']]
+    return (module, caller.f_locals)
+
+def embed_kernel(module=None, local_ns=None):
+    """Call this to embed an IPython kernel at the current point in your program. """
+    (caller_module, caller_locals) = caller_module_and_locals()
+    if module is None:
+        module = caller_module
+    if local_ns is None:
+        local_ns = caller_locals
+    # Only import .zmq when we really need it
+    from .zmq.ipkernel import embed_kernel as real_embed_kernel
+    real_embed_kernel(module, local_ns)

IPython/zmq/ipkernel.py

@@ -645,20 +645,7 b' def launch_kernel(*args, **kwargs):'
     return base_launch_kernel('from IPython.zmq.ipkernel import main; main()',
                               *args, **kwargs)
 
-def caller_module_and_locals():
-    """Returns (module, locals) of the caller"""
-    caller = sys._getframe(1).f_back
-    global_ns = caller.f_globals
-    module = sys.modules[global_ns['__name__']]
-    return (module, caller.f_locals)
-
-def embed_kernel(module=None, local_ns=None):
-    """Call this to embed an IPython kernel at the current point in your program. """
-    (caller_module, caller_locals) = caller_module_and_locals()
-    if module is None:
-        module = caller_module
-    if local_ns is None:
-        local_ns = caller_locals
+def embed_kernel(module, local_ns):
     app = IPKernelApp.instance(user_module=module, user_ns=local_ns)
     app.initialize([])
     app.start()