Update deprecated Python syntax and func references

[hristog]

Relevant Issue #
N/A

Description of the Change
This updates some deprecated Python v2 syntax and function references (particularly, apply; see https://docs.python.org/2/library/functions.html#non-essential-built-in-functions).

The justification is enabling better readabilty and clarity, as well as making strides towards updating the codebase to be in a state that'd be easily portable to Python v3.

Alternate Designs
N/A

Release Notes
N/A

[TheAspens]

@hristog - PR #4303 enabled support for both python2 and python3. Is there anything in this PR that should be retained or can it be closed?

[hristog]

Hi @TheAspens, thanks for checking!

Yes, I confirm the proposed changes implemented in #3722 are distinct from #4043, #3259 and #4070, and can be retained.
I couldn't find #4303 which you've referenced - I suppose the PR ID had a typo in it.

[TheAspens]

Your changes look good but I want to test it first. Could you merge the latest code from master into your branch so that I can easily confirm that it works correctly with python3 updates that were made recently? Thanks!

And you are correct - #4043 was the PR I meant to refer to.

[hristog]

I confirm I've now merged the latest master into my branch (and pushed, which has updated this PR as well), and I'm awaiting the completion of the code checks.

[hristog]

@TheAspens, I can see that all 4 automated checks have passed successfully.
Do you need me to do any further changes, related to this PR?

[TheAspens]

My apologies for the delay. I've tested setting up a new project and performing basic functions on it and it all looks good. Thanks for the contribution.

[hristog]

No problem at all. Thanks for confirming!