Technical guide
Create a .gitignore file
Write and share Git ignore rules, check which patterns match, and keep exceptions working without accidentally treating inline comments as patterns.
Explainer
Create nested directories in Python
Create missing parent directories with pathlib or os.makedirs, tolerate existing directories, and understand permissions, races, and path conflicts.
Explainer
Build a Python dictionary from two lists
Combine keys and values with dict and zip, reject mismatched lengths, handle duplicate keys, and avoid unexpected keys when filling missing values.
Explainer
Implement a singleton in Python
Compare module-level instances, metaclass caching, and __new__ in Python, including repeated initialization, thread safety, and testing trade-offs.
Explainer
Debug pytest tests with pdb and breakpoints
Set a breakpoint in a pytest test or enter pdb on failure, inspect variables, and understand capture behavior and PYTHONBREAKPOINT.
Explainer
Define custom exceptions in Python
Create application exceptions from Exception or a specific built-in type, preserve normal exception behavior, and expose structured error details.
Explainer
Delete items from a Python dictionary
Use del, pop, or popitem to remove dictionary entries, choose missing-key behavior, and delete several keys without mutating an active iteration.
Explainer
Delete files and directories in Python
Choose unlink, rmdir, or shutil.rmtree for the correct target, handle missing paths and symlinks, and understand when deletion bypasses the trash.
Technical guide
Delete a Git branch locally and on the remote
Delete local and remote branch refs separately, prune stale tracking refs, and check merge status and worktrees before removing a branch.
Technical guide
Split a subdirectory into a separate Git repository
Extract a directory and its relevant history with git-filter-repo or subtree split, then publish the new repository and update its dependencies.
Explainer
Determine an object’s type in Python
Use type for exact classes, isinstance for inheritance-aware checks, and issubclass for classes. Check supported operations directly when type is not the requirement.
Technical guide
Find the remote URL of a local Git repository
Inspect fetch and push URLs, distinguish configured URLs from rewritten URLs, and understand why origin is not a permanent record of the original clone.