Python
Command Line Arguments and Exit Codes
sys.argv holds what the user typed, stdout carries results, stderr carries problems, and the exit code tells the shell whether it worked.
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Python
Building Command Line Tools with argparse
argparse turns a description of your options into a parser, a validator and a help page. It is the standard way to give a Python script a real interfa...
Python
Testing with unittest
A test is a small program that checks another program. unittest ships with Python, finds your tests automatically and tells you exactly what broke.
Python
Debugging: Tracebacks, pdb and Strategy
Reading the traceback, forming a hypothesis and checking it. The debugger is a tool; the method is what actually finds the bug.
Python
Code Quality: PEP 8, Docstrings and Clean Code
Code is read far more often than it is written. Consistent style, honest names and clear structure are what make the second reading cheap.
Python
Type Hints: The Basics
Annotations describe what a function expects and returns. Python does not enforce them, and that is the point: they are documentation a tool can check...
Python
Advanced Typing: Generics, Protocol and TypedDict
Type variables let one function work with any type while keeping the relationship between input and output. Protocol describes a shape, and TypedDict...
Python
Complexity and Choosing Data Structures
Big-O describes how work grows with input size. Choosing the right container is worth more than every micro-optimisation combined.
Python
Profiling: timeit, cProfile and tracemalloc
Measure before optimising. Guessing where a program spends its time is wrong often enough that the habit is worth breaking permanently.
Python
Optimisation Techniques
Once the algorithm is right, a handful of techniques reliably help: build less, look up less, let C do the loop, and cache what repeats.
Python
Input Validation, Files and Secrets
Most security problems come from trusting input, trusting paths and storing secrets in the wrong place. Each has a standard, boring, correct answer.
Python
Dangerous Execution and Injection
eval, exec, shell commands, string built queries and pickle all take text and turn it into action. Each has a safe alternative that costs almost nothi...