IPython Notebook: Open-select file with GUI (Qt Dialog)

{
 "metadata": {
  "name": "",
  "signature": "sha256:dd9ac9500d76bd6e4f223aa5277e5008fc30d9ad1df9ccab4997b0cbe52860c7"
 },
 "nbformat": 3,
 "nbformat_minor": 0,
 "worksheets": [
  {
   "cells": [
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "##IPython Notebook: Open/select file with GUI (Qt Dialog)"
     ]
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "Often times it comes handy to select a file graphically. This can be easily done with a Qt dialog:"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "try:\n",
      "    from PySide import QtCore, QtGui\n",
      "except ImportError:\n",
      "    from PyQt4 import QtCore, QtGui\n",
      "\n",
      "def gui_fname(dir=None):\n",
      "    \"\"\"Select a file via a dialog and returns the file name.\n",
      "    \"\"\"\n",
      "    if dir is None: dir ='./'\n",
      "    fname = QtGui.QFileDialog.getOpenFileName(None, \"Select data file...\", \n",
      "            dir, filter=\"All files (*);; SM Files (*.sm)\")\n",
      "    return fname[0]"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [],
     "prompt_number": 1
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "However, running this function from an notebook causes the kernel to die (and restart):"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "full_fname = gui_fname()"
     ],
     "language": "python",
     "metadata": {},
     "outputs": []
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "Ok, this is espected because we need to setup the QT toolking integration.\n",
      "\n",
      "So, after restating the kernel, please skip the previous line and run the following instead:"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "%gui qt\n",
      "full_fname = gui_fname()\n",
      "%matplotlib inline"
     ],
     "language": "python",
     "metadata": {},
     "outputs": []
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "unfortunately we still have a kernel crash.\n",
      "\n",
      "As a workaround, I found that we can execute the GUI toolkit setup in a separate cell. \n",
      "\n",
      "In practice, after a kernel restart, skip the previous 2 code cells and execute this:"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "%gui qt"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [],
     "prompt_number": 2
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "Now you can execute the following cell as many times as you want and it will always display the *OpenFile* dialog without crashing:"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "%gui qt\n",
      "file_name = gui_fname()\n",
      "%matplotlib inline"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [],
     "prompt_number": 3
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "file_name"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 4,
       "text": [
        "u'C:/Data/Eitan/r6g_olympus.spc'"
       ]
      }
     ],
     "prompt_number": 4
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "> **Note**: In the previous cell I use the magic `matplotlib inline` because, while it is handy to load a file name via GUI, I still want my plots to be inline."
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [],
     "language": "python",
     "metadata": {},
     "outputs": []
    }
   ],
   "metadata": {}
  }
 ]
}

To view the notebook click here.