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
Reload Logstash configuration automatically
Enable automatic configuration reloads, understand pipeline restarts, and verify a change without assuming lossless handover.
Explainer
Install Postfix noninteractively on Ubuntu
Preseed debconf answers, install Postfix without prompts, and apply a deliberately scoped mail configuration before testing delivery.
Technical guide
Have Git set an upstream on the first push
Configure push.autoSetupRemote, distinguish publishing from branch-creation tracking, and troubleshoot cases where automatic setup does not apply.
Explainer
Back up and restore user crontabs
Export a user’s schedule safely, capture system jobs separately, and restore without accidentally replacing the wrong table.
Technical guide
Split a Git commit into smaller commits
Use interactive rebase to stop at a commit, unstage its changes, and rebuild a reviewable series without losing the original tree.
Explainer
Calculate Kubernetes CPU usage with Prometheus
Convert container CPU time into cores used, then compare usage with requests or limits without mixing Pods across namespaces.
Technical guide
Catch multiple exceptions in one Python handler
Use a tuple of exception classes when failures share a recovery path, and keep version differences and exception inheritance explicit.
Technical guide
Print colored terminal output in Node.js
Use ANSI sequences or Chalk, reset styles, and adapt color output to the destination instead of assuming every terminal or log file supports it.
Technical guide
Change the author of one Git commit
Amend author metadata without accidentally including staged changes, edit an older commit with rebase, and distinguish author identity from committer identity.