[Matplotlib-users] switching output formats within a function

[matthew a. <ma...@ca...>]

Hi

I'm writing a small script to plot my data, and I'd like to use a command 
line option to allow the same plot to be either displayed with GTK or 
output to postscript.

This means I have to switch matplotlib backends within the script.

Now by the time I know what option the user has chosen, I'm in a function:

def plotThings(options):
    matplotlib.use(options.plotbackend)
    from matplotlib.matlab import *

    plot(...)
    ...

and python complains

SyntaxWarning: import * only allowed at module level

It still works, but I think I'm on thin ice. And it doesn't work if I do:

def main():
    # ... parse options ...

    matplotlib.use(options.plotbackend)
    from matplotlib.matlab import *

    plotThings(options)

SyntaxWarning: import * only allowed at module level
NameError: global name 'plot' is not defined

The matplotlib docs say you need to specify the backend before importing 
matplotlib.matlab. But this seems a bit restrictive: what if I want to 
display a plot  on screen, and then output the same plot to postscript and 
print it? Normally imports are done only once at the top of a file, but 
I'd like to be able to switch backends anywhere.

What are your thoughts on this issue?

I've been using matplotlib for a while. It's the best python plotting tool 
I reckon. Thanks for contributing to free software.

Cheers and thanks,
Matthew.