Performance issues when upgrading from 3.7.1 to 3.7.4

https://codesandbox.io/s/brython-in-webworker-ss03z

Set in javascript

inputs['test'] = ["1"]

Processed in Brython webworker

l = inputs['test']
for i,v in enumerate(l):
  l[i] = v + " TEST"
outputs.list = l

v3.7.0 Brython Complete 181.6349999862723 <— Time to just execute brython script TOTAL TIME: 587.0599999907427 <— Time to transfer data via post message execute brython script and transfer back

v3.7.4 Brython Complete 4222.049999982119 <— Time to just execute brython script TOTAL TIME: 4548.055000021122 <— Time to transfer data via post message execute brython script and transfer back

[PierreQuentel]

I have found the reason : the culprit is the json module which is imported in the script.

Until version 3.7.1 it was a Brython-specific version of the stdlib module, built on top of Javascripts’s JSON object. Because of issues reported in #1116 and #1117, I had to replace it with the CPython stdlib package. Unfortunately it is much longer to import and this explains what you observe.

Instead of this package, you can still use the Javascript JSON object, which is available as the attribute JSON of browser.window. Instead of

import json
json.dumps(value)

you can use the much faster

from browser import window
window.JSON.stringify(value)

From 3.7.4 onwards, JSON is also an attribute of the javascript module.

[PierreQuentel]

I am closing this issue, once again many thanks for the report and the proposals. If you can develop a Javascript equivalent of the module, please submit a PR.