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Michael #1: Ubuntu 20.04 is out!
- Next LTS support version since 26th April 2018 (18.04).
- Comes with Python 3.8 included!
- Already upgraded all our servers, super smooth.
- Kernel has been updated to the 5.4 based Linux kernel, with additional support for Wireguard VPN, AUFS5, and improved support for IBM, Intel, Raspberry Pi and AMD hardware.
- Features the latest version of the GNOME desktop environment.
- Brings support for installing an Ubuntu desktop system on top of ZFS.
- 20.04 already an option on DigitalOcean ;)
Brian #2: Working with warnings in Python
- (Or: When is an exception not an exception?)
- Reuven Lerner
- Exceptions, the class hierarchy of exceptions, and warnings.
- “… most of the time, warnings are aimed at developers rather than users. Warnings in Python are sort of like the “service needed” light on a car; the user might know that something is wrong, but only a qualified repairperson will know what to do. Developers should avoid showing warnings to end users.”
- Python’s warning system …:
- It treats the warnings as a separate type of output, so that we cannot confuse it with either exceptions or the program’s printed text,
- It lets us indicate what kind of warning we’re sending the user,
- It lets the user indicate what should happen with different types of warnings, with some causing fatal errors, others displaying their messages on the screen, and still others being ignored,
- It lets programmers develop their own, new kinds of warnings.
- Reuven goes on to show how to use warnings in your code.
- using them
- creating custom warnings
Michael #3: Safer file writer
with open(filename, 'w') as fp:
- It’s using with, so it’s good right?
- Well the file itself may be overwritten and maybe corrupted
safer, you write almost identical code:
with safer.open(filename, 'w') as fp:
Brian #4: codespell
- codespell : Fix common misspellings in text files. It's designed primarily for checking misspelled words in source code, but it can be used with other files as well.
- I got a cool pull request against the cards project to add a pre-commit hook to run codespell. (Thanks Christian Clauss)
- codespell caught a documentation spelling error in cards, where I had spelled “arguments” as “arguements”. Oops.
- Spelling errors are annoying and embarrassing in code and comments, and distracting. Also hard to deal with using traditional spell checkers. So super glad this is a thing.
Michael #5: Austin profiler
- via Anthony Shaw
- Python frame stack sampler for CPython
- Profiles CPU and Memory!
- Why Austin?
- Written in pure C Austin is written in pure C code. There are no dependencies on third-party libraries.
- Just a sampler - fast: Austin is just a frame stack sampler. It looks into a running Python application at regular intervals of time and dumps whatever frame stack it finds.
- Simple output, powerful tools Austin uses the collapsed stack format of FlameGraph that is easy to parse. You can then go and build your own tool to analyse Austin's output.
- You could even make a player that replays the application execution in slow motion, so that you can see what has happened in temporal order.
- Small size Austin compiles to a single binary executable of just a bunch of KB.
- Easy to maintain Occasionally, the Python C API changes and Austin will need to be adjusted to new releases. However, given that Austin, like CPython, is written in C, implementing the new changes is rather straight-forward.
- Creates nice flame graphs
The Austin TUI is nice!
Web Austin is yet another example of how to use Austin to make a profiling tool. It makes use of d3-flame-graph to display a live flame graph in the web browser that refreshes every 3 seconds with newly collected samples.
Austin output format can be converted easily into the Speedscope JSON format. You can find a sample utility along with the TUI and Austin Web.
Brian #6: Numbers in Python
- Moshe Zadka
- A great article on integers, floats, fractions, & decimals
- They turn into floats very easily,
4.0, int → float
- don’t behave like the floating point numbers in theory
- don’t obey mathematical properties
- subtraction and addition are not inverses
0.1 + 0.2 - 0.2 - 0.1 !=
- addition is not associative
- My added comment: Don’t compare floats with ==, use pytest.approx or other approximation techniques.
- Kinda cool that they are there but be very careful about your input
- Algorithms on fractions can explode in time and to some extent memory.
- Generally better to use floats
- Good for financial transactions.
- Weird dependence on a global state variable, the context precision.
- Safer to use a local context to set the precision locally
>>> with localcontext() as ctx:
... ctx.prec = 10
... Decimal(1) / Decimal(7)
Unix is user friendly. It's just very particular about who its friends are. (via PyJoke)
If you put 1000 monkeys at 1000 computers eventually one will write a Python program. The rest will write PERL. (via @JamesAbel)