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

Question

When you perform the same analysis in a notebook on different data files, may be handy to graphically select a data file.
In my python scripts I usually implement a QT dialog that returns the file-name of the selected file:
from PySide import QtCore, QtGui
def gui_fname(dir=None):
"""Select a file via a dialog and return the file name.
"""
if dir is None: dir ='./'
fname = QtGui.QFileDialog.getOpenFileName(None, "Select data file...",
dir, filter="All files (*);; SM Files (*.sm)")
return fname[0]
However, running this function from an notebook
full_fname = gui_fname()
causes the kernel to die (and restart):
Interestingly, puttying this 3 command in 3 separate cells works
%matplotlib qt
full_fname = gui_fname()
%matplotlib inline
but when I put those commands in one single cell the kernel dies again.
This prevents to create a function like gui_fname_ipynb() that transparently allows selecting a file with a GUI.
For convenience, I created a notebook illustrating the problem:
Open/select file with GUI (Qt Dialog)
Any suggestion on how to execute a dialog for file selection from within an IPython Notebook?

Answer 1

Using Anaconda 5.0.0 on windows (Python 3.6.2, IPython 6.1.0), the following two options are both working for me.
OPTION 1: Entirely in a Jupyter notebook:
CELL 1:
%gui qt
from PyQt5.QtWidgets import QFileDialog
def gui_fname(dir=None):
"""Select a file via a dialog and return the file name."""
if dir is None: dir ='./'
fname = QFileDialog.getOpenFileName(None, "Select data file...",
dir, filter="All files (*);; SM Files (*.sm)")
return fname[0]
CELL 2:
gui_fname()
This is working for me but it seems a bit...fragile. If I combine these two things into the same cell, it crashes. Or if I omit the %gui qt, it crashes. If I "restart kernel and run all cells", it doesn't work. So I kinda like this other option...
MORE RELIABLE OPTION: Separate script that opens dialog box in a new process
(Based on mkrog code here.)
PUT THE FOLLOWING IN A SEPARATE PYTHON SCRIPT CALLED blah.py:
from sys import executable, argv
from subprocess import check_output
from PyQt5.QtWidgets import QFileDialog, QApplication
def gui_fname(directory='./'):
"""Open a file dialog, starting in the given directory, and return
the chosen filename"""
# run this exact file in a separate process, and grab the result
file = check_output([executable, __file__, directory])
return file.strip()
if __name__ == "__main__":
directory = argv[1]
app = QApplication([directory])
fname = QFileDialog.getOpenFileName(None, "Select a file...",
directory, filter="All files (*)")
print(fname[0])
...AND IN YOUR JUPYTER NOTEBOOK
import blah
blah.gui_fname()

Answer 2

I have a universal code where it does its job without any problem. Here is my sugestion:
try:
from tkinter import Tk
from tkFileDialog import askopenfilenames
except:
from tkinter import Tk
from tkinter import filedialog
Tk().withdraw() # we don't want a full GUI, so keep the root window from appearing
filenames = filedialog.askopenfilenames() # show an "Open" dialog box and return the path to the selected file
print (filenames)
hope it can be useful

Answer 3

This behaviour was a bug in IPython:
https://github.com/ipython/ipython/issues/4997
that was fixed here:
https://github.com/ipython/ipython/pull/5077
The function to open a gui dialog should work on current master and on the oncoming 2.0 release.
To date, the last 1.x version (1.2.1) does not include a backport of the fix.
EDIT: The example code still crashes IPython 2.x, see this issue.