#194 Events and callbacks in the Python language!

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Manage episode 269344608 series 1305988
By Michael Kennedy and Brian Okken. Discovered by Player FM and our community — copyright is owned by the publisher, not Player FM, and audio is streamed directly from their servers. Hit the Subscribe button to track updates in Player FM, or paste the feed URL into other podcast apps.

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Brian #1: An introduction to mutation testing in Python

  • Moshe Zadka
  • This article uses mutmut, but there are other mutation testing packages.
  • The example shows 3 methods, and one test case that actually hits 100% code coverage.
  • The mutmut is used and finds 16 surviving mutants.
  • “Mutation testing algorithmically modifies source code and checks if any "mutants" survived each test. Any mutant that survives the unit test is a problem: it means that a modification to the code, likely introducing a bug, was not caught by the standard test suite.”
  • “For each mutation test, mutmut modified portions of your source code that simulates potential bugs. An example of a modification is changing a > comparison to >= to see what happens. If there is no unit test for this boundary condition, this mutation will "survive": this is a potential bug that none of the tests will detect.”
  • Cool example of how to check mission critical parts of your code and the tests around them above and beyond code coverage.
  • BTW, mutmut is also used codechalleng.es in the challenges asking users to write the tests.

Michael #2: asynq

  • From Quora, a little old but still interesting and active
  • A library for asynchronous programming in Python with a focus on batching requests to external services.
  • Also provides seamless interoperability with synchronous code, support for asynchronous context managers, and tools to make writing and testing asynchronous code easier.
  • Developed at Quora and is a core component of Quora's architecture.
  • The most important use case for asynq is batching.
  • asynq's asynchronous functions are implemented as Python generator functions. Every time an asynchronous functions yields one or more Futures, it cedes control the asynq scheduler,

Brian #3: redis: Beyond the Cache

  • Guy Royse
  • Some cool examples with Python code of using redis for more than a cache.
    • as a queue, with rpush and blpop
    • pub/sub, with publish and psubscribe
    • data streaming, with xadd and xread
    • as a search engine
    • and of course, as a primary in-memory database
  • examples use aioredis to access with async/await

Michael #4: LittleTable

  • Discovered as part of my multi-key dictionary quest (more on this later)
  • By Paul McGuire
  • A Python module to give ORM-like access to a collection of objects
  • Provides a low-overhead, schema-less, in-memory database access to a collection of user objects.
  • In addition to basic ORM-style insert/remove/query/delete access to the contents of a Table, littletable offers:
    • simple indexing for improved retrieval performance, and optional enforcing key uniqueness
    • access to objects using indexed attributes
    • simplified joins using '+' operator syntax between annotated Tables
    • the result of any query or join is a new first-class littletable Table

Brian #5: pytest-timeout

  • listener suggestion
  • This is essential, I think.
  • Make sure no test runs longer than a certain number of seconds.
  • You can set a global timeout either via command line or via a config file.
  • You can specify different times for specific tests via a mark decorator
  • Great stopgap to make sure no test runs forever.

Michael #6: Events

  • Call me, maybe
  • by Nicola Iarocci
  • Adds event subscription and callback to the Python language
  • Based on C# language’s events, provides a handy way to declare, subscribe to and fire events.
  • Encapsulates the core to event subscription and event firing and feels like a “natural” part of the language.
  • Example:
 >>> def something_changed(reason): ... print(f"something changed because {reason}") >>> from events import Events >>> events = Events() >>> events.on_change += something_changed 
  • Multiple callback functions can subscribe to the same event. When the event is fired, all attached event handlers are invoked in sequence.
 >>> events.on_change('it had to happen') 'something changed because it had to happen' 

Extras:

Michael:

  • Finished the memory management course, coming soon. Started one on Python design patterns

Brian:

Joke:

https://xkcd.com/327/

199 episodes