#137: Advanced Python testing and big-time diffs

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:

• Pynsource: Reverse engineer Python source code into UML diagrams (via Anders Klint)
• Language Bar chart race (via Josh Thurston)
• My Local maximum appearance.

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 <business idea>? B: That seems too niche. K: What’s “niche” mean? B: It’s the girl version of “nephew”.