Created some prose documentation about best practices #11657
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In how far should this be part of The how-to section? I suppose it's not really clear for a user where to look for such content if there are two documents with FAQs? It also seems that what is written here as part of "Creating your own plotting functions" is already present in the Coding Styles section of the Usage tutorial. |
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My thinking is that this "Best Practices" document should merely be a summary. Meanwhile, documents like the style guide should be much more detailed and in-depth. Also, the section for the function design might not make sense to be in a "style" guide now that we would have this best practices guide. |
| fig.clear() | ||
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| Now, only one figure object is ever made, and it is cleaned of any plots | ||
| at each iteration, so the memory usage will not grow. |
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... or just call plt.close("all") at the end of the loop. This avoids having to factor out figure creation from the main loop.
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👍 for close. It's more clear and (currently) even faster.
%%timeit
fig = plt.figure()
for i in range(50):
plt.plot([1, 3, 2])
plt.savefig('test.png')
fig.clear()
3.12 s ± 53.8 ms per loop (mean ± std. dev. of 7 runs, 1 loop each)
%%timeit
for i in range(50):
plt.figure()
plt.plot([1, 3, 2])
plt.savefig('test.png')
plt.close()
2.75 s ± 27.1 ms per loop (mean ± std. dev. of 7 runs, 1 loop each)
It's also a good general reminder, not only with looping: Close your pyplot figures when your done.
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What prompted me to make this document was when someone came to me with a script that was growing in memory significantly and they did something like this. I don't remember if they were calling plt.close() or not, but recycling the figure definitely solves that problem.
| Now you want to make this plot for each of your data files. One might just | ||
| put the above code into a for-loop over all of your filenames. However, you | ||
| will eventually encounter a warning ``More than X figures hae been opened.``. | ||
| With enough looping, Python can eventually run out of memory, and calling |
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Proposed rewording:
With enough looping, Python can eventually run out of memory because the
pyplotfigure manger keeps a reference to every created figure.
| fig.clear() | ||
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| Now, only one figure object is ever made, and it is cleaned of any plots | ||
| at each iteration, so the memory usage will not grow. |
There was a problem hiding this comment.
👍 for close. It's more clear and (currently) even faster.
%%timeit
fig = plt.figure()
for i in range(50):
plt.plot([1, 3, 2])
plt.savefig('test.png')
fig.clear()
3.12 s ± 53.8 ms per loop (mean ± std. dev. of 7 runs, 1 loop each)
%%timeit
for i in range(50):
plt.figure()
plt.plot([1, 3, 2])
plt.savefig('test.png')
plt.close()
2.75 s ± 27.1 ms per loop (mean ± std. dev. of 7 runs, 1 loop each)
It's also a good general reminder, not only with looping: Close your pyplot figures when your done.
| For nontrivial plots, it may make sense to create your own plotting | ||
| functions for easy reuse. Here are some guidelines: | ||
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| * Have an ``ax`` positional argument as the first argument. |
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This pattern should be discussed.
IMO ax as the first positional argument is not a good choice. I would rather use something like:
def my_plotter(data1, data2, ax=None, param_dict=None):
if ax is None:
ax = plt.gca()
...
Usage patterns:
my_plotter(data1, data2) # similar to pyplot
my_plotter(data1, data2, ax=ax)
See also #9111
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This definitely should be discussed, because there is some discussion of a new interface that would have this pattern as the default for all plotting functions. ping @tacaswell @efiring
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I'm going to close this. Much of this info has been incorporated elsewhere. It is also a grab-bag a-la the FAQ page and I really don't think we want grab-bag pages like this. If there is material here that is still relevant, please feel free to rebase and reopen or make a new PR. Thanks! |
PR Summary
Add a "best practices" guide, and added a couple entries to it based on questions asked by attendees at SciPy.
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