Develop Reference

Is %matplotlib inline still needed?

There are many resources that explains why %matplotlib inline is necessary to display plots inline. E.g. Purpose of %matplotlib inline. However, I feel that it is no longer necessary if we are using later version of IPython in your Jupyter Notebook. This is because I can display plots inline with or without running %matplotlib inline (each time I restart my kernel, IPython version I am using is 7.17.0). My hunch is that perhaps inline backend is activated by default for recent versions.
When I run %matplotlib to check the current backend on a new session, it says Qt5Agg. After running %matplotlib inline, when I check again by running %matplotlib, it displays the same Qt5Agg. This makes me think that %matplotlib inline is redundant as it's not changing anything. I haven't changed any IPython config myself btw.
However, I don't see any official documentation saying that inline backend is activated by default for IPython versions x.x.x+. I found this and this Github issue that was close to what I was trying to find but it doesn't fully confirm "You no longer need to run %matplotlib inline if your IPython version is x.x.x+ as it is the default behaviour". I looked through IPython recent release notes, but doesn't seem to confirm the hypothesis.
Is my hunch right? If so, what IPython versions it is not required? Is there any official documentation saying that? If not, how come I am able to plot inline without running %matplotlib inline?
This may seem as a possible duplication of Why don't I need “%matplotlib inline” in my jupyter notebook?. I wasn't able to confirm my hunch from this thread.

The answer is basically no.
There's a fine bug report that explains why.
The only ones who would need to do it are users of the non-object-oriented interface of matplotlib. Users who do not use pyplot.
If you import pyplot with the standard import matplotlib.pyplot as plt, or even if you import pandas, then it isn't necessary to execute %matplotlib inline.

The only reason %matplotlib inline is used is to render any matplotlib diagrams even if the plt.show() function is not called.
However, even if %matplotlib inline is not used, Jupyter will still display the Matplotlib diagram as an object, with something like matplotlib.lines.Line2D object at 0x0392A9D0 appearing before it in the console.
The end point is that it is not necessary anymore, however, it is still convention to keep your code clean and call on the plot that you made, and definitely recommended.

matplotlib pyplot Invalid DISPLAY variable

While importing and attempting the following:
import matplotlib
from matplotlib import pyplot as plt
plt.plot([1,2,3],[1,4,9])
plt.show()
I get the following error. How do I fix? I am running Python 2.7, and notebook version 4.1.0. Thank you.
RuntimeError: Invalid DISPLAY variable

When running a jupyter notebook on a server, the server may not even be able to display the plot. The usual solution would be to use a non-interactive backend. In case of a jupyter notebook this would be done by adding
%matplotlib inline
at the top of the notebook, such that graphics are shown as png images.

Seaborn Not Working from Script in Ubuntu

Python 2.7.12
matplotlib 1.5.1
Seaborn 0.8.0
Ubuntu 16.04, with the pip package manager.
I have tried running the codes in seaborn gallery.
They simply do not work when I run a script from terminal. They just say
"seaborn.axisgrid.FacetGrid object at 0x7fdfa554c1d0". Matplotlib works though.
Seaborn does work, however, from the jupyter notebook in my browser. But even then, the plots are really bland and simple, not many interactive customisation options. Nothing like the attractive, feature rich and aesthetically pleasing things you see on tutorials, or the gallery.
Can someone tell me what's wrong?

To show a plot, you need to call
plt.show()
where plt is import matplotlib.pyplot as plt.

ipython notebook on linux VM running matplotlib interactive with nbagg

I want buttons and other interactive matplotlib objects to appear from within my ipython notebook.
Here is what I've done:
Installed http://datasciencetoolbox.org, it is a vagrant box with ipython installed and version 1.3.1 of matplotlib.
I needed to upgrade matplotlib to the latest version, because it has this capability to do inline interactive plots. What's new in Matplotlib 1.4.1
I needed to run sudo apt-get install pkg-config and
sudo pip install matplotlib --upgradein order to get that going.
Then, in order to produce the nice (i.e. error-free) screenshot below, I went into the .ipython/dst-profile/ipython_notebook_config.py file and erased the line about IPKernelApp.pylab='inline' to be able to run the matplotlib.use('nbagg') command.
Then I was able to create the screenshot below. However, things still look poor. Those buttons are not buttons. That is an image of buttons. Please advise on how to make those buttons come to life!
Oh... and check this out if this helps you help me.
Thanks!

Basically you are facing two issues
the %pylab inlinecall overrides the matplotlib.use('nbagg')call, to use the inline backend instead of the nbagg backend which you are actually wanting. If you use a recent version of IPython (2.3) you can directly use %matplotlib nbagg (or %matplotlib notebook) to load the nbagg backend instead of your %pylabcall.
once you enabled the nbagg backend you will need to explicitly show it, ie. add a plt.show() call at the end of your script -> Update: with IPython 2.3.1 this is no longer needed (thanks #tcaswell for the hint)
With this you get the interactive matplotlib experience embedded in the IPython notebook. However, a quick try of your code does't yield to the desired result. The Button reacts and the callback is executed but the print call doesn't show anything. Anyway, to see that it's working try the following simple example (requires IPython 2.3):
%matplotlib nbagg
from matplotlib.widgets import Button
import matplotlib.pyplot as plt
def callback(event):
plt.text(event.xdata, event.ydata, 'clicked')
f,a = plt.subplots(1)
b1 = Button(a,'Button1')
b1.on_clicked(callback)
plt.show()
Btw. it is highly recommended to use %matplotlib instead of %pylab as later leads to some side effects, see here.

in Ipython notebook / Jupyter, Pandas is not displaying the graph I try to plot

I am trying to plot some data using pandas in Ipython Notebook, and while it gives me the object, it doesn't actually plot the graph itself. So it looks like this:
In [7]:
pledge.Amount.plot()
Out[7]:
<matplotlib.axes.AxesSubplot at 0x9397c6c>
The graph should follow after that, but it simply doesn't appear. I have imported matplotlib, so that's not the problem. Is there any other module I need to import?

Note that --pylab is deprecated and has been removed from newer builds of IPython, The recommended way to enable inline plotting in the IPython Notebook is now to run:
%matplotlib inline
import matplotlib.pyplot as plt
See this post from the ipython-dev mailing list for more details.

Edit:Pylab has been deprecated please see the current accepted answer
Ok, It seems the answer is to start ipython notebook with --pylab=inline.
so ipython notebook --pylab=inline
This has it do what I saw earlier and what I wanted it to do.
Sorry about the vague original question.

With your import matplotlib.pyplot as plt just add
plt.show()
and it will show all stored plots.

simple after importing the matplotlib you have execute one magic if you have started the ipython as like this
ipython notebook
%matplotlib inline
run this command everything will be shown perfectly

start ipython with ipython notebook --pylab inline ,then graph will show inline.

import matplotlib as plt
%matplotlib as inline

All you need to do is to import matplotlib.
import matplotlib.pyplot as plt