Bug report

Bug summary

Calling input inside a key_press_event results either in a RuntimeError or causes the terminal and canvas to freeze. Presumably, this is because the input to input triggers further on_key_press calls (although this issue also appears to happen when the figure is not in focus so I am actually not sure if that is the reason). I am looking for a work around.

Code for reproduction

import matplotlib.pyplot as plt

plt.ion()

fig, ax = plt.subplots()

def on_key_press(event):
    if event.key == 'enter':
        ans = input('Provide some text to print and press enter:\n')
        # ans = 'foo'
        ax.text(event.xdata, event.ydata, ans)
        fig.canvas.draw_idle()

cid = fig.canvas.mpl_connect('key_press_event', on_key_press)

Actual outcome

Traceback (most recent call last):
  File "/home/paul/.virtualenvs/test3_netgraph/lib/python3.5/site-packages/matplotlib/cbook/__init__.py", line 389, in process
    proxy(*args, **kwargs)
  File "/home/paul/.virtualenvs/test3_netgraph/lib/python3.5/site-packages/matplotlib/cbook/__init__.py", line 227, in __call__
    return mtd(*args, **kwargs)
  File "/home/paul/src/netgraph/netgraph/input_block.py", line 16, in on_key_press
    ans = input('Provide some text to print and press enter:\n')
RuntimeError: can't re-enter readline

Expected outcome

The expected outcome can be simulated by commenting out the input call and uncommenting the ans = 'foo' line in the MWE.

Matplotlib version

• Operating system: Ubuntu 17.04
• Matplotlib version: 2.1.0
• Matplotlib backend (print(matplotlib.get_backend())): TkAgg
• Python version: 3.5.3
• Jupyter version (if applicable): na
• Other libraries: numpy, ipython and their dependencies

Installed everything via pip.