Explainer
Log an exception with its traceback in Python
Use logger.exception or exc_info to preserve exception tracebacks, and configure a hook for uncaught main-thread exceptions.
Explainer
Read environment variables in Python
Read required and optional environment variables, convert configuration values, and load a .env file during local development.
Explainer
Get the index and value in a Python for loop
Use enumerate to iterate with a counter, set the starting number, and combine it with zip or dictionary items.
Technical guide
Add an empty directory to a Git repository
Keep a directory in a Git checkout with a placeholder file, or create it during setup. Use ignore rules that allow the placeholder to remain tracked.
Explainer
Add keys to a Python dictionary
Insert or replace dictionary entries with assignment, merge values with update, and set a default only when a key is missing.
Explainer
Append text to a file in Python
Open a file in append mode, write complete lines, read appended content, and distinguish flushing buffers from syncing data to disk.
Explainer
Assert approximate equality with pytest
Compare floating-point results with pytest.approx, choose meaningful tolerances, and handle sequences, dictionaries, NumPy arrays, and NaN.
Explainer
Assert that Python code raises an exception with pytest
Use pytest.raises to check exception types, match error messages, inspect exception details, and avoid assertions that never run.
Explainer
Reorder columns in a pandas DataFrame
Select columns in a new order, move a single column with pop and insert, and understand how selection differs from reindex.
Explainer
Customize timestamps in Python logging
Set logging datefmt, include milliseconds, choose local time or UTC, and supply formatter settings through dictConfig.
Explainer
Check whether a Python list is empty
Use a list’s truth value to test for emptiness, distinguish an empty list from None, and handle NumPy arrays separately.
Explainer
Check whether an object has an attribute in Python
Use hasattr and getattr to check Python attributes, retrieve defaults, and handle properties or dynamic lookup without hiding unexpected errors.