#137 Advanced Python testing and big-time diffs

Python Bytes - A podcast by Michael Kennedy and Brian Okken - Mondays

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Technology

Sponsored by Rollbar: https://pythonbytes.fm/rollbar

Brian #1: Comparing the Same Project in Rust, Haskell, C++, Python, Scala and OCaml

  • Tristan Hume, writing about a university project
  • Teams of up to 3 people, multi month, write a Java to x86 compiler in language of choice
  • Needed to pass both known and unknown tests.
  • Secret tests to be run after submission encouraged teams to add more testing than provided.
  • Nothing but standard libraries, and no parsing libraries, even if in standard.
  • Lines of code
    • Rust baseline
    • Haskell: 1-1.6x
    • C++: 1.4x
    • Rust (another team): 3x
    • Scala: 0.7 x
    • OCaml: 1-1.6x
    • Python: about half the size
  • Python version
    • one person
    • used metaprogramming
    • more extra features than any other team
    • passed all public and secret tests

Michael #2 : Pylustrator is a program to style your matplotlib plots

  • via Len Wanger
  • Pylustrator is a program to style your matplotlib plots for publication.
  • Subplots can be resized and dragged around by the mouse, text and annotations can be added.
  • Changes can be saved to the initial plot file as python code.

Brian #3: MongoDB 4.2

  • Distributed Transactions
    • extends multi-document ACID transactions across documents, collections, dbs in a replica set, and sharded cluster.
  • Field Level Encryption
    • encryption done on client side
    • satisfies GDPR by allowing customer key destruction rendering server data on customer useless.
    • system administration can be done with no exposure to private data

Michael #4: Deep Difference and search of any Python object/data

  • via François Leblanc
  • DeepDiff: Deep Difference of dictionaries, iterables, strings and other objects. It will recursively look for all the changes.
  • Lots of nice touches:
    • List difference ignoring order or duplicates
    • Report repetitions
    • Exclude certain types from comparison
    • Exclude part of your object tree from comparison
    • Significant Digits
  • DeepSearch: Search for objects within other objects.
  • DeepHash: Hash of ANY python object based on its contents even if the object is not considered hashable! DeepHash is supposed to be deterministic in order to make sure 2 objects that contain the same data, produce the same hash.

Brian #5: Advanced Python Testing

  • Josh Peak
  • “This article is mostly for me to process my thoughts but also to pave a path for anyone that wants to follow a similar journey on some more advanced python testing topics.”
  • Learning journey (including some great podcasts and an awesome book on testing)
  • Testing tools
    • basic test structure
    • adding black to testing with pytest-black
    • linting with pylint
      • including a very cool speed up trick to only lint modified files.
    • flake8, including docstring checking
    • tox.ini modifications
    • code coverage goals and how to ratchet up to that goal with --cov-fail-under
      • cool learning: “Increase code coverage by testing more code OR deleting code.”
    • fixtures for database connections
    • utilizing mocks, spies, stubs, and monkey patches, including pytest-mock
    • pytest-vcr to save network interactions and replay them in future test runs, resulting in a 10x speedup.
  • Lots of links and tangents possible from this article.

Michael #6: Understanding Python's del

  • via Kevin Buchs
  • Official docs
  • General confusion of what this does
  • Looks like memory management, and it mostly isn’t
  • Primary use: remove an item from a list given its index instead of its value or from a dictionary given its key: del person['profession'] # person is a dict
  • del statement can also be used to remove slices from a list del lst[2:4]
  • del can also be used to delete entire variables: del variable
  • Recently covered how The CPython Bytecode Compiler is Dumb. Proactive dels could help.

Extras

Michael:

Jokes

Optimist: The glass is half full. Pessimist: The glass is half empty. Programmer: The glass is twice as large as necessary.

Pragmatist: allowing room for requirements oversights, scope creep, and schedule overrun.

From “The Upside” with Kevin Hart and Bryan Cranston (watched it last night): K: Would you invest in [HTML_REMOVED]? B: That seems too niche. K: What’s “niche” mean? B: It’s the girl version of “nephew”.