add missing sys import

docs/examples/parallel/Parallel Magics.ipynb

@@ -1,313 +1,323 b''
 {
  "metadata": {
   "name": "Parallel Magics"
  },
  "nbformat": 3,
  "worksheets": [
   {
    "cells": [
     {
      "cell_type": "heading",
      "level": 1,
      "source": [
       "Using Parallel Magics"
      ]
     },
     {
      "cell_type": "markdown",
      "source": [
       "IPython has a few magics for working with your engines.",
       "",
       "This assumes you have started an IPython cluster, either with the notebook interface,",
       "or the `ipcluster/controller/engine` commands."
      ]
     },
     {
      "cell_type": "code",
      "collapsed": false,
      "input": [
       "from IPython import parallel",
       "rc = parallel.Client()",
       "dv = rc[:]",
       "dv.block = True",
       "dv"
      ],
      "language": "python",
      "outputs": []
     },
     {
      "cell_type": "markdown",
      "source": [
       "The parallel magics come from the `parallelmagics` IPython extension.",
       "The magics are set to work with a particular View object,",
       "so to activate them, you call the `activate()` method on a particular view:"
      ]
     },
     {
      "cell_type": "code",
      "collapsed": true,
      "input": [
       "dv.activate()"
      ],
      "language": "python",
      "outputs": []
     },
     {
      "cell_type": "markdown",
      "source": [
       "Now we can execute code remotely with `%px`:"
      ]
     },
     {
      "cell_type": "code",
      "collapsed": false,
      "input": [
       "%px a=5"
      ],
      "language": "python",
      "outputs": []
     },
     {
      "cell_type": "code",
      "collapsed": false,
      "input": [
       "%px print a"
      ],
      "language": "python",
      "outputs": []
     },
     {
      "cell_type": "code",
      "collapsed": false,
      "input": [
       "%px a"
      ],
      "language": "python",
      "outputs": []
     },
     {
      "cell_type": "code",
      "collapsed": false,
      "input": [
+      "with dv.sync_imports():",
+      "    import sys"
+     ],
+     "language": "python",
+     "outputs": []
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
       "%px print >> sys.stderr, \"ERROR\""
      ],
      "language": "python",
      "outputs": []
     },
     {
      "cell_type": "markdown",
      "source": [
       "You don't have to wait for results:"
      ]
     },
     {
      "cell_type": "code",
      "collapsed": true,
      "input": [
       "dv.block = False"
      ],
      "language": "python",
      "outputs": []
     },
     {
      "cell_type": "code",
      "collapsed": false,
      "input": [
       "%px import time",
       "%px time.sleep(5)",
       "%px time.time()"
      ],
      "language": "python",
      "outputs": []
     },
     {
      "cell_type": "markdown",
      "source": [
       "But you will notice that this didn't output the result of the last command.",
       "For this, we have `%result`, which displays the output of the latest request:"
      ]
     },
     {
      "cell_type": "code",
      "collapsed": false,
      "input": [
       "%result"
      ],
      "language": "python",
      "outputs": []
     },
     {
      "cell_type": "markdown",
      "source": [
       "Remember, an IPython engine is IPython, so you can do magics remotely as well!"
      ]
     },
     {
      "cell_type": "code",
      "collapsed": false,
      "input": [
       "dv.block = True",
       "%px %pylab inline"
      ],
      "language": "python",
      "outputs": []
     },
     {
      "cell_type": "markdown",
      "source": [
       "`%%px` can also be used as a cell magic, for submitting whole blocks.",
       "This one acceps `--block` and `--noblock` flags to specify",
       "the blocking behavior, though the default is unchanged.",
       ""
      ]
     },
     {
      "cell_type": "code",
      "collapsed": true,
      "input": [
       "dv.scatter('id', dv.targets, flatten=True)",
       "dv['stride'] = len(dv)"
      ],
      "language": "python",
      "outputs": []
     },
     {
      "cell_type": "code",
      "collapsed": false,
      "input": [
       "%%px --noblock",
       "x = linspace(0,pi,1000)",
       "for n in range(id,12, stride):",
       "    print n",
       "    plt.plot(x,sin(n*x))",
       "plt.title(\"Plot %i\" % id)"
      ],
      "language": "python",
      "outputs": []
     },
     {
      "cell_type": "code",
      "collapsed": false,
      "input": [
       "%result"
      ],
      "language": "python",
      "outputs": []
     },
     {
      "cell_type": "markdown",
      "source": [
       "It also lets you choose some amount of the grouping of the outputs with `--group-outputs`:",
       "",
       "The choices are:",
       "",
       "* `engine` - all of an engine's output is collected together",
       "* `type` - where stdout of each engine is grouped, etc. (the default)",
       "* `order` - same as `type`, but individual displaypub outputs are interleaved.",
       "  That is, it will output the first plot from each engine, then the second from each,",
       "  etc."
      ]
     },
     {
      "cell_type": "code",
      "collapsed": false,
      "input": [
       "%%px --group-outputs=engine",
       "x = linspace(0,pi,1000)",
       "for n in range(id,12, stride):",
       "    print n",
       "    plt.figure()",
       "    plt.plot(x,sin(n*x))",
       "plt.title(\"Plot %i\" % id)"
      ],
      "language": "python",
      "outputs": []
     },
     {
      "cell_type": "markdown",
      "source": [
       "When you specify 'order', then individual display outputs (e.g. plots) will be interleaved:"
      ]
     },
     {
      "cell_type": "code",
      "collapsed": false,
      "input": [
       "%%px --group-outputs=order",
       "x = linspace(0,pi,1000)",
       "for n in range(id,12, stride):",
       "    print n",
       "    plt.figure()",
       "    plt.plot(x,sin(n*x))",
       "plt.title(\"Plot %i\" % id)"
      ],
      "language": "python",
      "outputs": []
     },
     {
      "cell_type": "heading",
      "level": 2,
      "source": [
       "Single-engine views"
      ]
     },
     {
      "cell_type": "markdown",
      "source": [
       "When a DirectView has a single target, the output is a bit simpler (no prefixes on stdout/err, etc.):"
      ]
     },
     {
      "cell_type": "code",
      "collapsed": true,
      "input": [
       "def generate_output():",
       "    \"\"\"function for testing output",
       "    ",
       "    publishes two outputs of each type, and returns something",
       "    \"\"\"",
       "    ",
       "    import sys,os",
       "    from IPython.core.display import display, HTML, Math",
       "    ",
       "    print \"stdout\"",
       "    print >> sys.stderr, \"stderr\"",
       "    ",
       "    display(HTML(\"<b>HTML</b>\"))",
       "    ",
       "    print \"stdout2\"",
       "    print >> sys.stderr, \"stderr2\"",
       "    ",
       "    display(Math(r\"\\alpha=\\beta\"))",
       "    ",
       "    return os.getpid()",
       "",
       "dv['generate_output'] = generate_output"
      ],
      "language": "python",
      "outputs": []
     },
     {
      "cell_type": "code",
      "collapsed": true,
      "input": [
       "e0 = rc[-1]",
       "e0.block = True",
       "e0.activate()"
      ],
      "language": "python",
      "outputs": []
     },
     {
      "cell_type": "code",
      "collapsed": false,
      "input": [
       "%px generate_output()"
      ],
      "language": "python",
      "outputs": []
     }
    ]
   }
  ]
 }
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