[Tutor] loading modules only when needed and PEP 008

[Eric Walstad]

Hi Tim,
Tim Michelsen wrote:
> Hello fellow Pythonistas,
> I have a question concerning import statements.
...
> it takes a lot 
> of time for a TKinter-GUI to start up. And this start-up time is even 
> longer when matplotlib is imported
....
> a optimized version would be:
> import sys
> 
> plot_data = 'yes' # option: yes/no
> 
> if plot_data == 'yes':
> 	import matplotlib
> else:
> 	pass
...
> How would you handle such a case?
> What is recommended in such a case?
> Does anyone have experience with this?
Beware that code later in your module that calls matplotlib.foo() may 
fail if plot_data is not 'yes'.  When I do this sort of thing I like to 
move my imports into my functions/methods.  The 'main' code then 
conditionally calls the function/method.  All the code in the function 
safely assumes that the import has been done but code in the calling 
function assumes the import hasn't been done.

-----
if plot_data:
     show_plot_data(mydata)

-----
def show_plot_data(data):
     "load matplotlib and show the user the data"
     import matplotlib
     ...do stuff with matplotlib...
-----

And as we are talking about style, note that your
else:
     pass
isn't really necessary but it does make it explicitly clear that you are 
choosing not to do anything if the plot_data isn't 'yes'.  Are those 
tabs you're using?  Four spaces are preferred, according to the style guide.