Inner Working of PYTHON

INTRODUCTION TO PYTHON

Python is an interpreted, high-level programming language that uses a multi-step execution process that convert source code into executable instructions.

PYTHON EXECUTION FLOW

Source Code (Python file ‘.py’) —> Lexical Analysis (Tokenization) —> Parsing (Concrete Syntax Tree ‘CST ‘) —> AST Generation (Abstract Syntax Tree) —> Bytecode Compilation (Platform-independent intermediate code) —> Bytecode Caching (.pyc files) —> Python Virtual Machine (‘PVM ‘/ Runtime Engine) —> Program Output (Final Execution Result)

Source Code (Python file ‘.py’) - Human-readable Python code with comments, whitespace, and syntax.

Lexical Analysis (Tokenization) - Breaks code into tokens: keywords, identifiers, operators, literals.

Parsing (Concrete Syntax Tree ‘CST ‘) - Creates grammatical structure tree including all syntax elements.

AST Generation (Abstract Syntax Tree) - Removes comments, whitespace, redundant syntax. Keeps only logical structure.

Bytecode Compilation (Platform-independent intermediate code) - Low-level instructions for Python Virtual Machine.

Bytecode Caching (.pyc files) - Cached in __pycache__ directory for imported modules
Format: filename.cpython-.pyc.

Python Virtual Machine (‘PVM ‘/ Runtime Engine) - Executes bytecode instructions with dynamic typing and memory management.

Program Output (Final Execution Result) - Console output, file operations, GUI displays, etc.

CHARACTERISTICS

Dynamic Typing: Types determined at runtime, not compile-time.

Platform Independent: Bytecode runs on any system with Python.

Interpreted: Bytecode is interpreted, not compiled to machine code.

Stack-based: PVM uses stack operations for execution.

IMPLEMENTATIONS

CPython (Standard)

Jython (Java-based)

IronPython (C#/.NET)

PyPy (JIT compiler)

Stackless (Microthreads)