If you want to run code in a kernel from another Python program, the easiest way is to connect a BlockingKernelManager. The best example of this right now is Paul Ivanov's vim-ipython client, or IPython's own terminal client.
The gist:
- ipython kernels write JSON connection files, in
IPYTHONDIR/profile_<name>/security/kernel-<id>.json, which contain information necessary for various clients to connect and execute code.
- KernelManagers are the objects that are used to communicate with kernels (execute code, receive results, etc.).
*
A working example:
In a shell, do ipython kernel (or ipython qtconsole, if you want to share a kernel with an already running GUI):
$> ipython kernel
[IPKernelApp] To connect another client to this kernel, use:
[IPKernelApp] --existing kernel-6759.json
This wrote the 'kernel-6759.json' file
Then you can run this Python snippet to connect a KernelManager, and run some code:
from IPython.lib.kernel import find_connection_file
from IPython.zmq.blockingkernelmanager import BlockingKernelManager
# this is a helper method for turning a fraction of a connection-file name
# into a full path. If you already know the full path, you can just use that
cf = find_connection_file('6759')
km = BlockingKernelManager(connection_file=cf)
# load connection info and init communication
km.load_connection_file()
km.start_channels()
def run_cell(km, code):
# now we can run code. This is done on the shell channel
shell = km.shell_channel
print
print "running:"
print code
# execution is immediate and async, returning a UUID
msg_id = shell.execute(code)
# get_msg can block for a reply
reply = shell.get_msg()
status = reply['content']['status']
if status == 'ok':
print 'succeeded!'
elif status == 'error':
print 'failed!'
for line in reply['content']['traceback']:
print line
run_cell(km, 'a=5')
run_cell(km, 'b=0')
run_cell(km, 'c=a/b')
The output of a run:
running:
a=5
succeeded!
running:
b=0
succeeded!
running:
c=a/b
failed!
---------------------------------------------------------------------------
ZeroDivisionError Traceback (most recent call last)
/Users/minrk/<ipython-input-11-fb3f79bd285b> in <module>()
----> 1 c=a/b
ZeroDivisionError: integer division or modulo by zero
see the message spec for more information on how to interpret the reply. If relevant, stdout/err and display data will come over km.iopub_channel, and you can use the msg_id returned by shell.execute() to associate output with a given execution.
PS: I apologize for the quality of the documentation of these new features. We have a lot of writing to do.
