Python typing cheatsheet & other stuff

Nice cheatsheet, not mypy-specific: Type hints cheat sheet (Python 3) — Mypy 0.910 documentation

Otherwise:

• Functions that may return None:
  • x = 1 if True else None, x would be Optional[int]
• Iterables / Sequences:
  • Iterable is anything usable inside a for
  • Sequence is anything that supports len()
  • For example:

    def f(ints: Iterable[int]) -> List[str]:
    return [str(x) for x in ints]
    

python unittests through CLI

From docu ¹:

python -m unittest test_module1 test_module2
python -m unittest test_module.TestClass
python -m unittest test_module.TestClass.test_method

When I’m in the directory with the test_xy.py files, running python3 -m unittest runs all of them. I can also do python3 -m unittest test_xy for that file, and python3 -m unittest test_xy.TestXY.test_specific_thing.

Debugging python from CLI through breakpoints

Found this, and it’s freaking awesome: Debugging by starting a REPL at a breakpoint is fun

Sample from there:

def make_request():
    result = requests.get("https://google.com")
    import ipdb; ipdb.set_trace()

There’s the default pdb, there’s ipdb that has to be installed.

Adding

import ipdb; ipdb.set_trace()

anywhere in the code launches a typical debug window that can be used to look into the vars etc.

Just used this for the first time to debug a python program that was running on a remote server and failing, but not locally.

SO much better than print(f"XXX {i}") and friends!

Nice tutorial about its usage: Better Python Debugging With IPDB

• n - next line in current method (=“step over”)
• s - next line of executable code anywhere (=“step into”)
• c - continue till next breakpoint
• r - continue till function returns (would be nice to learn how to do this in pycharm btw!)
• a - args - print arguments current function received
• b - adds breakpoint to locations
  • b filename.py:234
  • b <function>
  • b 123 - line in current file

Full documentation here: 26.2. pdb — The Python Debugger — Python 2.7.18 documentation

Python serializing Enums by declaring them as subclass of str

My main issue with Enum classes was that serialization is weird, especially if you’re dumping parameters. Tried again, found this: python - Serialising an Enum member to JSON - Stack Overflow

TL;DR class EnumDerivedClass(str, Enum)

import json
from enum import Enum

class LogLevel(str, Enum):
    DEBUG = 'DEBUG'
    INFO = 'INFO'

print(LogLevel.DEBUG)
print(json.dumps(LogLevel.DEBUG))
print(json.loads('"DEBUG"'))
print(LogLevel('DEBUG'))

will output

LogLevel.DEBUG
"DEBUG"
DEBUG
LogLevel.DEBUG

Google Presentations work in progress slides

“Folie überspringen” is a much better way to do what I did with setting a yellow background color - easy to see and worst case scenario it’ll just get skipped

Tensorboard and no data because wrong input folder

If you run tensorboard on a non-existing folder, you’ll get no feedback about it anywhere?.. No data on Tensorboard itself, nothing useful in CLI.