8e80217e59
Former-commit-id:a02aeb236c[formerly9f19e3f712] [formerly06a8b51d6d[formerly 64fa9254b946eae7e61bbc3f513b7c3696c4f54f]] Former-commit-id:06a8b51d6dFormer-commit-id:3360eb6c5f
143 lines
5 KiB
ReStructuredText
Executable file
143 lines
5 KiB
ReStructuredText
Executable file
.. _mpl-shell:
|
|
|
|
**********************************
|
|
Using matplotlib in a python shell
|
|
**********************************
|
|
|
|
By default, matplotlib defers drawing until the end of the script
|
|
because drawing can be an expensive operation, and you may not want
|
|
to update the plot every time a single property is changed, only once
|
|
after all the properties have changed.
|
|
|
|
But when working from the python shell, you usually do want to update
|
|
the plot with every command, eg, after changing the
|
|
:func:`~matplotlib.pyplot.xlabel`, or the marker style of a line.
|
|
While this is simple in concept, in practice it can be tricky, because
|
|
matplotlib is a graphical user interface application under the hood,
|
|
and there are some tricks to make the applications work right in a
|
|
python shell.
|
|
|
|
|
|
.. _ipython-pylab:
|
|
|
|
Ipython to the rescue
|
|
=====================
|
|
|
|
Fortunately, `ipython <http://ipython.scipy.org/dist>`_, an enhanced
|
|
interactive python shell, has figured out all of these tricks, and is
|
|
matplotlib aware, so when you start ipython in the *pylab* mode.
|
|
|
|
.. sourcecode:: ipython
|
|
|
|
johnh@flag:~> ipython -pylab
|
|
Python 2.4.5 (#4, Apr 12 2008, 09:09:16)
|
|
IPython 0.9.0 -- An enhanced Interactive Python.
|
|
|
|
Welcome to pylab, a matplotlib-based Python environment.
|
|
For more information, type 'help(pylab)'.
|
|
|
|
In [1]: x = randn(10000)
|
|
|
|
In [2]: hist(x, 100)
|
|
|
|
it sets everything up for you so interactive plotting works as you
|
|
would expect it to. Call :func:`~matplotlib.pyplot.figure` and a
|
|
figure window pops up, call :func:`~matplotlib.pyplot.plot` and your
|
|
data appears in the figure window.
|
|
|
|
Note in the example above that we did not import any matplotlib names
|
|
because in pylab mode, ipython will import them automatically.
|
|
ipython also turns on *interactive* mode for you, which causes every
|
|
pyplot command to trigger a figure update, and also provides a
|
|
matplotlib aware ``run`` command to run matplotlib scripts
|
|
efficiently. ipython will turn off interactive mode during a ``run``
|
|
command, and then restore the interactive state at the end of the
|
|
run so you can continue tweaking the figure manually.
|
|
|
|
There has been a lot of recent work to embed ipython, with pylab
|
|
support, into various GUI applications, so check on the ipython
|
|
mailing `list
|
|
<http://projects.scipy.org/mailman/listinfo/ipython-user>`_ for the
|
|
latest status.
|
|
|
|
.. _other-shells:
|
|
|
|
Other python interpreters
|
|
=========================
|
|
|
|
If you can't use ipython, and still want to use matplotlib/pylab from
|
|
an interactive python shell, eg the plain-ole standard python
|
|
interactive interpreter, or the interpreter in your favorite IDE, you
|
|
are going to need to understand what a matplotlib backend is
|
|
:ref:`what-is-a-backend`.
|
|
|
|
|
|
|
|
With the TkAgg backend, that uses the Tkinter user interface toolkit,
|
|
you can use matplotlib from an arbitrary python shell. Just set your
|
|
``backend : TkAgg`` and ``interactive : True`` in your
|
|
:file:`matplotlibrc` file (see :ref:`customizing-matplotlib`) and fire
|
|
up python. Then::
|
|
|
|
>>> from pylab import *
|
|
>>> plot([1,2,3])
|
|
>>> xlabel('hi mom')
|
|
|
|
should work out of the box. Note, in batch mode, ie when making
|
|
figures from scripts, interactive mode can be slow since it redraws
|
|
the figure with each command. So you may want to think carefully
|
|
before making this the default behavior.
|
|
|
|
For other user interface toolkits and their corresponding matplotlib
|
|
backends, the situation is complicated by the GUI mainloop which takes
|
|
over the entire process. The solution is to run the GUI in a separate
|
|
thread, and this is the tricky part that ipython solves for all the
|
|
major toolkits that matplotlib supports. There are reports that
|
|
upcoming versions of pygtk will place nicely with the standard python
|
|
shell, so stay tuned.
|
|
|
|
.. _controlling-interactive:
|
|
|
|
Controlling interactive updating
|
|
================================
|
|
|
|
The *interactive* property of the pyplot interface controls whether a
|
|
figure canvas is drawn on every pyplot command. If *interactive* is
|
|
*False*, then the figure state is updated on every plot command, but
|
|
will only be drawn on explicit calls to
|
|
:func:`~matplotlib.pyplot.draw`. When *interactive* is
|
|
*True*, then every pyplot command triggers a draw.
|
|
|
|
|
|
The pyplot interface provides 4 commands that are useful for
|
|
interactive control.
|
|
|
|
:func:`~matplotlib.pyplot.isinteractive`
|
|
returns the interactive setting *True|False*
|
|
|
|
:func:`~matplotlib.pyplot.ion`
|
|
turns interactive mode on
|
|
|
|
:func:`~matplotlib.pyplot.ioff`
|
|
turns interactive mode off
|
|
|
|
:func:`~matplotlib.pyplot.draw`
|
|
forces a figure redraw
|
|
|
|
When working with a big figure in which drawing is expensive, you may
|
|
want to turn matplotlib's interactive setting off temporarily to avoid
|
|
the performance hit::
|
|
|
|
|
|
>>> #create big-expensive-figure
|
|
>>> ioff() # turn updates off
|
|
>>> title('now how much would you pay?')
|
|
>>> xticklabels(fontsize=20, color='green')
|
|
>>> draw() # force a draw
|
|
>>> savefig('alldone', dpi=300)
|
|
>>> close()
|
|
>>> ion() # turn updating back on
|
|
>>> plot(rand(20), mfc='g', mec='r', ms=40, mew=4, ls='--', lw=3)
|
|
|
|
|
|
|