Python and PySide2: small recipes

Testing a function that reads input and prints output

Replace input() and sys.stdout with unittest.mock.patch:

import io
from unittest.mock import patch

user_input = ['6 1']
expected_output = '...'  # exactly what the function prints

with patch('builtins.input', side_effect=user_input):
    with patch('sys.stdout', new=io.StringIO()) as output:
        dodawanie(84, 7)
        self.assertEqual(expected_output, output.getvalue())

More: How to test input processing in Python 3

Upgrade all outdated pip packages

(venv) $ pip list --outdated
(venv) $ pip list --outdated --format=freeze \
               | grep -v '^\-e' | cut -d = -f 1 \
               | xargs -n1 pip install -U

Source: How to upgrade all Python packages with pip

Reverse a string

txt = "Hello World"[::-1]

Save memory with generators

Generators return a lazy iterator instead of building the whole list in memory: Optimizing Memory Usage in Python Applications

Don’t write command-line menus, generate them

Instead of writing a command-line menu by hand, use hug or typer — it is like implementing a REST interface for your command-line program. See Don’t write command-line interfaces (generate them).

PySide2: open dialogs with exec()

window = QUiLoader().load("form/asset_ed.ui")
window.exec()

PySide2: iterate over files in resources

Compile the resource file:

pyside2-rcc resources.qrc > resources.py

Iterate over a resource directory:

import resources

it = QDirIterator(':/icon/icons8/')
while it.hasNext():
    self.icon.addItem(QIcon(it.next()), '')

Dark theme for Jupyter Notebook

pip install jupyterthemes
jt -t monokai -fs 95 -altp -tfs 11 -nfs 115 -cellw 88% -T

Restore the default theme:

jt -r

Project: jupyter-themes