Simplify code syntax in several places

[uriyyo]

Hi guys,
I enjoy to work with FastAPI, it's really great 👍

What was done in scope of this PR:

• Use comprehension instead of loops.
• Use __init__ method of a base class where it possible.
• Replace usage of dict.setdefault method with collections.defaultdict.

[codecov]

Codecov Report

Merging #1753 into master will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##            master     #1753   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files          235       235           
  Lines         6987      6985    -2     
=========================================
- Hits          6987      6985    -2     

Impacted Files	Coverage Δ
fastapi/applications.py	100.00% <100.00%> (ø)
fastapi/dependencies/utils.py	100.00% <100.00%> (ø)
fastapi/encoders.py	100.00% <100.00%> (ø)
fastapi/openapi/constants.py	100.00% <100.00%> (ø)
fastapi/security/http.py	100.00% <100.00%> (ø)

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[acutaia]

Add another comprehension

[acutaia]

Add another comprhension

[jahhhsueihh]

في أربعاء، 22 يوليو، 2020 في 12:05 ص، كتب Angelo Cutaia < notifications@github.com>:

…

***@***.**** approved this pull request. — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#1753 (review)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AQIQIRI6FDMMKZR25EWXMZLR4XYILANCNFSM4PDNA2UA> pjjjiii.

[tiangolo]

Thanks for your effort @uriyyo ! 🚀

And thanks for the discussion everyone. ☕

Nice trick with the defaultdict! 🤓

I reverted a couple of the changes, some lists, because I find it more explicit with an explicit list than with a list comprehension when the logic starts to have some extra complexity.

For some of the classes, I had intentionally not used super() at some point after some breaking changes in Starlette, and because there wasn't that much shared code, I had decided to duplicate the small bits, given I still had to implement the custom local logic.

And for the security classes, they don't really have any internal logic, they only set attributes, so I found it more explicit to duplicate those little bits that still needed some customization for each specific class in several cases than to pass everything to super(), as it seems to hide some virtual complexity that doesn't really exist. The amount of code is quite similar, and it's still needed to override some things (like the Pydantic models). So I prefer to keep it that way.

Thanks for your contribution! 🚀 🍰