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# Running mlab scripts

Mlab, like the rest of Mayavi, is an interactive application. If you are not already in an interactive environment (see next paragraph), to interact with the figures or the rest of the drawing elements, you need to use the `show()` function. For instance, if you are writing a script, you need to call `show()` each time you want to display one or more figures and allow the user to interact with them.

## Using mlab interactively

Using IPython mlab instructions can be run interactively, or in scripts using IPython‘s `%run` command:

    In [1]: %run my_script

You need to start IPython with the -wthread option (when installed with EPD, the pylab start-menu link does this for you). In this environment, the plotting commands are interactive: they have an immediate effect on the figure, alleviating the need to use the `show()` function.

Mlab can also be used interactively in the Python shell of the mayavi2 application, or in any interactive Python shell of wxPython-based application (such as other Envisage-based applications, or SPE, Stani’s Python Editor).

## Using together with Matplotlib’s pylab

If you want to use Matplotlib’s pylab with Mayavi’s mlab in IPython you should:

> - if your IPython version is greater than 0.8.4: start IPython with the following options:

>       $ ipython -pylab -wthread

> - elsewhere, start IPython with the -wthread option:

>       $ ipython -wthread

>   and before importing pylab, enter the following Python commands:

>       >>> import matplotlib
>       >>> matplotlib.use('WxAgg')
>       >>> matplotlib.interactive(True)

If you want matplotlib and mlab to work together by default in IPython, you can change you default matplotlib backend, by editing the ~/.matplotlib/matplotlibrc to add the following line:

    backend     : WXAgg

## In scripts

Mlab commands can be written to a file, to form a script. This script can be loaded in the Mayavi application using the File->Open file menu entry, and executed using the File->Refresh code menu entry or by pressing `Control-r`. It can also be executed during the start of the Mayavi application using the `-x` command line switch.

As mentioned above, when running outside of an interactive environment, for instance with python myscript.py, you need to call the `show()` function (as shown in the demo above) to pause your script and have the user interact with the figure.

You can also use `show()` to decorate a function, and have it run in the event-loop, which gives you more flexibility:

    from enthought.mayavi import mlab
    from numpy import random

    @mlab.show
    def image():
       mlab.imshow(random.random((10, 10)))

With this decorator, each time the image function is called, mlab makes sure an interactive environment is running before executing the image function. If an interactive environment is not running, mlab will start one and the image function will not return until it is closed.

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