How Python Runs Programs

Process: source code -> compiled byte code -> PVM (Python Virtual Machine) runs byte code

Performance loss: compilation + extra work in running virtual machineImplementation variations: CPython (the standard); Jython; IronPython; Stackless Python; PyPy (with JIT compiler).Optimization: Cython (Python/C hybrid)Frozen binary: PyInstaller

Python Conceptual Hierarchy

programs > modules > statements > expressions > objects

Core Data Types

• Number (int, float, complex, decimal, fraction, boolean)
• String
• List
• Dictionary
• Tuple
• File
• Set
• None
• Program units: function, module, class

Typing

Variable is created during value assignment. Variable itself has no type information, it simply points to an object and the object can be any type. Python's typing is:

• Dynamic: type is determined automatically at runtime, not declared
• Strong: every object has two header fields: type designator; reference counter.

Objects are garbage-collected, programmer doesn't have to free them.