How Python Works

By Jane Smith

Python is a high-level, interpreted programming language known for its clear syntax and readability. Created by Guido van Rossum and first released in 1991, Python has grown to become one of the most popular programming languages in the world.

The Python interpreter converts your source code into bytecode, which is then executed by the Python Virtual Machine (PVM). This process involves several stages: lexical analysis, parsing, compilation, and interpretation.

Lexical Analysis

The first step is tokenizing the source code. The lexer (or tokenizer) reads characters from the source file and groups them into tokens — the smallest meaningful units of a Python program, such as keywords, identifiers, operators, and literals.

Parsing

The parser takes the stream of tokens and builds an Abstract Syntax Tree (AST), which represents the grammatical structure of your code. Python's grammar is defined in a formal specification and the parser checks that your code conforms to it.

import ast
tree = ast.parse("x = 1 + 2")
print(ast.dump(tree))

This outputs a tree structure showing how Python internally represents your code, with nodes for assignments, binary operations, and so on.