No plot window in matplotlib

Question

I just installed matplotlib in Ubuntu 9.10 using the synaptic package system. However, when I try the following simple example

>>> from pylab import plot;
>>> plot([1,2,3],[1,2,3])
[<matplotlib.lines.Line2D object at 0x9aa78ec>]

I get no plot window. Any ideas on how to get the plot window to show?

Answer 1

pylab.show() works but blocks (you need to close the window).

A much more convenient solution is to do pylab.ion() (interactive mode on) when you start: all (the pylab equivalents of) pyplot.* commands display their plot immediately. More information on the interactive mode can be found on the official web site.

I also second using the even more convenient ipython -pylab (--pylab, in newer versions), which allows you to skip the from … import … part (%pylab works, too, in newer IPython versions).

Answer 2

If you are starting IPython with the --pylab option, you shouldn't need to call show() or draw(). Try this:

ipython  --pylab=inline

Answer 3

Try this:

import matplotlib
matplotlib.use('TkAgg') 

BEFORE import pylab

Answer 4

Any errors show up? This might an issue of not having set the backend. You can set it from the Python interpreter or from a config file (.matplotlib/matplotlibrc) in you home directory.

To set the backend in code you can do

import matplotlib
matplotlib.use('Agg')

where 'Agg' is the name of the backend. Which backends are present depend on your installation and OS.

http://matplotlib.sourceforge.net/faq/installing_faq.html#backends

http://matplotlib.org/users/customizing.html

Answer 5

Modern IPython uses the "--matplotlib" argument with an optional backend parameter. It defaults to "auto", which is usually good enough on Mac and Windows. I haven't tested it on Ubuntu or any other Linux distribution, but I would expect it to work.

ipython --matplotlib

Answer 6

You can type

import pylab
pylab.show()

or better, use ipython -pylab.