Java
PreparedStatement and SQL Injection Prevention in Java
Concatenating input into SQL lets a caller rewrite your query. Bound parameters make that structurally impossible.
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Java
JDBC Transactions and Batch Operations
A transaction makes several statements succeed or fail together, and batching turns many round trips into one.
Java
Unit Testing Fundamentals in Java
A unit test runs a small piece of code with known input and asserts the result, automatically and repeatedly.
Java
Test Doubles and Mocking Concepts in Java
A test double stands in for a real dependency so a unit can be tested in isolation, quickly and predictably.
Python
Introduction to Python
Python is a high level, dynamically typed, interpreted language whose whole design goal is that a program should be as easy to read as it was to write...
Python
Installing Python and Running Your First Program
Install Python, check the version, meet the REPL, write a script and understand the difference between interactive mode and script mode.
Python
How Python Runs Your Code
Source code is compiled to bytecode and the Python Virtual Machine executes it. Knowing that explains __pycache__, import speed and most confusing err...
Python
Python Syntax and Structure
Indentation defines blocks, statements end at the line break, and a short set of rules about comments, keywords and identifiers covers everything else...
Python
Variables, Assignment and Constants in Python
A Python variable is a name bound to an object, not a box holding a value. That one distinction explains multiple assignment, swapping, dynamic typing...
Python
Python Data Types: The Complete Map
Python ships with a small set of built in types. Sorting them by three questions - single value or container, ordered or not, changeable or not - make...
Python
Numbers in Python: int, float, complex and bool
Integers are unbounded, floats are binary approximations, division always produces a float, and bool is quietly an integer. Each of those facts change...
Python
Mutability, Identity and Type Checking
type() names the class, id() names the object and isinstance() answers the question you usually meant to ask. Together they explain every aliasing sur...