Delay bleach import to optimise import time

[cdeil]

I'm looking a bit into why Python and Panel imports and startup are slow on my Macbook M1 and hacking on Panel apps I have a slow edit - run cycle. I get weird results unrelated to Panel, even import pandas sometimes takes 10-20 seconds and then on further executions just 0.7 seconds - maybe file caching or antivirus or something else - I haven't been able to identify the problem yet.

However, using tuna and these commands:

time PYTHONPROFILEIMPORTTIME=1 python -c 'import panel' 2> panel_import.log
tuna panel_import.log

I see that a few percent of the Panel import time is from

panel/panel/util/__init__.py

Line 26 in 46e0639

import bleach

where you import https://pypi.org/project/bleach/

Is it feasible / advisable to delay that import and only do it if needed, which I presume is if someone creates a HTML pane with non-default sanitize_html=True?

[philippjfr]

Seems very sensible, yes.

[cdeil]

x-ref bokeh/bokeh#13638 and https://stackoverflow.com/questions/77769896/profile-why-python-imports-are-slow-on-macos

[philippjfr]

Could it be the bytecode file (.pyc) generation?

[cdeil]

Could it be the bytecode file (.pyc) generation?

No. The pyc files are only generated once per environment and cached in site-packages, but I see import panel go back from taking 1 second to many seconds with a given environment simply when coming back the next day (or partial degradation after a few hours, it's not deterministic).

[philippjfr]

Got you, that's pretty bizarre indeed. Does sound like a security scan type thing.

[philippjfr]

Based on my timing import bleach takes about 31.8 ms on my machine, so I'm a little on the fence about whether making the import lazy is worth it in this case.

[MarcSkovMadsen]

Wow. That is a lot.

[philippjfr]

31 ms or the timings reported above?

[MarcSkovMadsen]

31ms for something only used in edge cases is a lot.

[philippjfr]

I wouldn't call it an edge case, it's used for all HTML, Markdown and ReactiveHTML based components.

[philippjfr]

Sorry guess for HTML/Markdown it is behind the sanitize parameter and therefore indeed an edge case but ReactiveHTML is not an edge case.

[hoxbro]

Even though it is not an edge case for ReactiveHTML, I still think we should not do any imports unless they are absolutely necessary.

For a hvplot-only user, it does not make any sense that Bleach is imported.

I also think this will make it possible to remove it from the build packages.