Add warning for few workers

[ethanwharris]

Before submitting

• Was this discussed/approved via a Github issue? (no need for typos and docs improvements)
• Did you read the contributor guideline, Pull Request section?
• Did you make sure to update the docs?
• Did you write any new necessary tests?
• If you made a notable change (that affects users), did you update the CHANGELOG?

What does this PR do?

Fixes #1322

• adds a warning when a data loader with only a few (<= 2) workers is used. Could potentially use a higher number? or just warn when num workers is zero?

PR review

Anyone in the community is free to review the PR once the tests have passed.
If we didn't discuss your PR in Github issues there's a high chance it will not be merged.

Did you have fun?

Make sure you had fun coding 🙃

[pep8speaks]

Hello @ethanwharris! Thanks for updating this PR.

There are currently no PEP 8 issues detected in this Pull Request. Cheers! 🍻

Comment last updated at 2020-04-04 18:20:18 UTC

[codecov]

Codecov Report

Merging #1378 into master will increase coverage by 0%.
The diff coverage is 100%.

@@          Coverage Diff           @@
##           master   #1378   +/-   ##
======================================
  Coverage      92%     92%           
======================================
  Files          63      63           
  Lines        3317    3320    +3     
======================================
+ Hits         3042    3045    +3     
  Misses        275     275           

[Borda]

LGTM 🚀

[jeremyjordan]

LGTM

[carlosgmartin]

@ethanwharris Is there a way to disable this warning?

[ethanwharris]

@carlosgmartin You should be able to use a warning filter to disable the warnings: https://docs.python.org/3/library/warnings.html#overriding-the-default-filter

Hope that helps 😃