interact + plotting with ipywidgets 6.0.0 produces many graphs or none

The following code worked for me in the previous version of ipywidgets (5.whatever-was-most-recent). By “worked” I mean it produced one plot, and dragging the slider updated that plot, with only one line shown on the plot at a time. If relevant, I’m using Chrome on OS X.

import matplotlib.pyplot as plt
%matplotlib inline
from ipywidgets import interact

def f(n):
    plt.plot([0,1,2],[0,1,n])
interact(f,n=(0,10))

I just updated to 6.0.0, cleared my browser cache, and relaunched everything. Now I get a new plot inserted vertically below the old one every time I drag the slider around.

I tried

import matplotlib.pyplot as plt
%matplotlib inline
from ipywidgets import interact

def f(n):
    plt.plot([0,1,2],[0,1,n])
interact(f,n=(0,10))

instead, and the plot does not update when the slider is dragged.

Changing %matplotlib inline to %matplotlib notebook and adding plt.clf() before the plot line sometimes works, but also sometimes just produces a blank plot when I drag the slider around.

Here’s some system information; I’m happy to provide more:

{'commit_hash': '5c9c918',
 'commit_source': 'installation',
 'default_encoding': 'UTF-8',
 'ipython_path': '/Users/mglerner/anaconda3/envs/nodev_up/lib/python3.6/site-packages/IPython',
 'ipython_version': '5.1.0',
 'os_name': 'posix',
 'platform': 'Darwin-15.6.0-x86_64-i386-64bit',
 'sys_executable': '/Users/mglerner/anaconda3/envs/nodev_up/bin/python',
 'sys_platform': 'darwin',
 'sys_version': '3.6.0 |Anaconda custom (x86_64)| (default, Dec 23 2016, '
                '13:19:00) \n'
                '[GCC 4.2.1 Compatible Apple LLVM 6.0 (clang-600.0.57)]'}

In [2]: matplotlib.__version__ Out[2]: '2.0.0'

I then tried updating a few things to the conda-forge version, including matplotlib. The results of the update are below, but the update did not fix the behavior.

`╰─➤ conda update ipython matplotlib jupyter numpy -c conda-forge 1 ↵ Fetching package metadata … Solving package specifications: .

Package plan for installation in environment /Users/mglerner/anaconda3/envs/nodev_up:

The following NEW packages will be INSTALLED:

blas:         1.1-openblas       conda-forge
libgfortran:  3.0.0-0            conda-forge
olefile:      0.44-py36_0        conda-forge
openblas:     0.2.19-1           conda-forge

The following packages will be UPDATED:

freetype:     2.5.5-2                        --> 2.7-1                              conda-forge
ipython:      5.1.0-py36_1                   --> 5.3.0-py36_0                       conda-forge
libpng:       1.6.27-0                       --> 1.6.28-0                           conda-forge
matplotlib:   2.0.0-np111py36_0              --> 2.0.0-np111py36_2                  conda-forge
numpy:        1.11.3-py36_0                  --> 1.11.3-py36_blas_openblas_200      conda-forge [blas_openblas]
pillow:       4.0.0-py36_0                   --> 4.0.0-py36_2                       conda-forge
scipy:        0.18.1-np111py36_1             --> 0.18.1-np111py36_blas_openblas_201 conda-forge [blas_openblas]

The following packages will be SUPERCEDED by a higher-priority channel:

jupyter:      1.0.0-py36_3                   --> 1.0.0-py36_0                       conda-forge
scikit-learn: 0.18.1-np111py36_1             --> 0.18-np111py36_blas_openblas_203   conda-forge [blas_openblas]

Proceed ([y]/n)? `

After doing so, the behavior was unchanged.

[jasongrout]

@mglerner - it seems I was mistaken above - you can use %matplotlib inline, but you’ll still need to explicitly show the plot. This works fine:

import matplotlib.pyplot as plt
from ipywidgets import interact
%matplotlib inline

def f(n):
    plt.plot([0,1,2],[0,1,n])
    plt.show()
interact(f,n=(0,10))

[jasongrout]

It sounds like we’ve solved this issue - the inline backend won’t work now for interacts, but we should directly use plt.show instead, so let’s close this issue and open others for other issues.

Thanks again @mglerner for reporting this!