serhii.net

Stumbled yet again¹ on mentions of IPython and decided to look into it, prev. assumption being that it’s the same or almost the same thing as Jupyter Notebook. (Also the i in ipdb stands for IPython-enabled, apparently).

It’s not., it’s a separate interactive superset of the Python cli that’s runnable by itself through python3 -m IPython.

Which in turn feels like a better / more interactive shell that can also do magic commands (%xxx) that I’ve seen in Google Colab / Jupyter; additionally understands bash stuff as-is and does other cool stuff. Definitely worth looking into.

ALSO the same article¹ mentions a way of using IPython inside ipdb, quoting:

ipdb> from IPython import embed
ipdb> embed() # drop into an IPython session.
        # Any variables you define or modify here
        # will not affect program execution

To run a program with ipdb without editing the source and dropping in an ipdb prompt when if it breaks from shell:

python3 -m ipdb script.py

Took another look at the official docu 26.2. pdb — The Python Debugger — Python 2.7.18 documentation:

• p prints the expression following, pp pretty-prints it.

Pressing u / d moves you through the individual frames of the stack.

Also TODO look into using it to run stuff and debug automatically on fail, without editing the source code.¹

An Inverted index - Wikipedia is a mapping from content to its location/name, as opposed to the usual case of name-to-content. One use is searching.

Recap

This is part two of 211209-1354 Python testing basics with poetry and pytest. Fixtures scopes work similarly to the various setup/teardown functions of unittest, can be per module/class/etc.

Failure

Expecting a test to fail

@pytest.mark.xfail(reason="Reason why it's supposed to fail")
def test_...

Expecting a test to raise an exception

For a specific exception, you assert that it raises that exception type and then can do asserts on the exception that is raised.

def test_whatever():
  with pytest.raises(Exception) as excinfo:
    raise Exception("oh no")
  assert str(excinfo.value) == "oh no"

Regex also works (example directly from pytest.raises() API Reference

>>> with pytest.raises(ValueError, match=r'must be \d+$'):
...     raise ValueError("value must be 42")

## Services (skipped, see below)
### Creating fixtures that get used automatically
```python
@pytest.fixture(autouse=True)
def skip_servicetest(request, run_services):
  if request....
    pytest.skip("skipped because X")

Using the filesystem

pyfakefs creates a fake filesystem that gets used transparently.

from pyfakefs.fake_filesystem import FakeFilesystem

@pytest.fixture
def common_fs(fs: FakeFilesystem):
  fs.create_dir(Path("/tmp/common"))
  fs.create_file("/tmp/common")

def test_filesystem_fixture(common_filesystem):
  assert os.path.exists("/tmp/common")
  assert os.path.exists("/tmp/not_there") == False

General hints

red-green-refactor

A development approach from TDD.

1. Red - Write a test, it fails
   • Forces us to think about what we want to develop and how do we want to use the interface we’re about to implement.
2. Green - Make it pass (as fast as possible)
   • If it’s simple, just type it
   • If it’s harder, make a note and write the quickest solution that makes the test pass
3. Refactor - Spend time to make the implementation correct.

F.I.R.S.T Principles

Tests should be:

• Fast (encourages us to run them frequently, which increases confidence in the code)
• Independent (not influence each other)
• Repeatable (in any environment)
• Self-validating (a failing test should give enough info about what’s wrong¹)
• Timely written (just before the production code)²

Arrange-Act-Assert (3A)

3A is a common pattern for structuring tests.

• Arrange -> Create objects / prepare the environment
• Act -> Simulate behaviour
• Assert -> Check the results

In a test this would look like this:

string = "ABc"

result = string.upper()

assert result == "ABC"

import this

A coworker reminded be of this gem; quoting him:

The order is important. My favourite one is ’explicit is better than implciit'

Had a big repo, wanted to clone only some folders.

The setup below automatically fetched the subfolders I added to the sparse-checkout set.

git clone --filter=blob:none --no-checkout --branch main ssh://git@me.me/my/repo.git
cd myrepo
git sparse-checkout init --cone
git sparse-checkout set "activitywatch" "friends" ".task" ".timewarrior"

https://gohugo.io/tools/search/

It boils down to creating an index (json) then using something to search in it client side

Once an index is built, Lunr seems the way to do with this: https://lunrjs.com/docs/lunr.Query.html#~Clause

It seems flexible enough, including ability to search inside taxonomies.

From SO¹, if both are JSON serializable objects, you can use json:

from json import loads, dumps
from collections import OrderedDict

def to_dict(input_ordered_dict):
    return loads(dumps(input_ordered_dict))

Qtile scripting

Scripting Commands — Qtile 0.1.dev50+ga708c8c.d20211209 documentation has a lot more interesting stuff than the ones exposed through “vanilla” config, finally figured out how to use them:

def test(qtile):
    qtile.cmd_to_layout_index(0)

# ...
Key([mod, ctrl], "apostrophe",  lazy.function(test))

It’s in the docu¹ but I missed its significance on first read, then saw hints in a github config².

The qtile object passed as the first argument is exactly the QTile from scripting.

Qtile switching to a layout by id

To parametrize it, you have to let it return a callable function:

def switch_to(ly_id: int):
    def cb(qtile):
        qtile.cmd_to_layout_index(ly_id)
    return cb

# ...
Key([mod, ctrl], "apostrophe",  lazy.function(switch_to(0))), 

More fun with qtile scripting

I don’t see this mentioned in the docu, but the attributes can be found in the source of libqtile.core.manager — Qtile 0.1.dev50+ga708c8c.d20211209 documentation.

If you mess up config.py and restart qtile and most of your keybindings aren’t working, if you’re lucky you still have a terminal open. From it, you can fix config.py, then restart via qtile shell -> restart().