Python Execution Pipeline

Source → Tokens → AST → Bytecode → CPython VM → Memory Model → GIL

1 / 30

steps

Stage 1 of 6·Lexer / Tokenizer

step 1

Source file

add.py

1def add(x, y):

2 result = x + y

3 return result

KEYWORDNAMEOPINDENT/DEDENTNEWLINE

Token stream — 0 tokens

Scanning…

Speednormal

The Python interpreter's first step is the lexer (tokenizer). It reads the raw .py file as a stream of characters and groups them into tokens — the vocabulary of the language. No structure is understood yet; the lexer only recognizes individual words and symbols.

Pipeline

Lexerchars → tokens

Parsertokens → AST

CompilerAST → bytecode

CPython VMbytecode → execution

MemoryPyObject + refcount

GIL / CPUeval loop + cache

Example

# The function we're tracing

def add(x, y):

result = x + y

return result

# Calling it

add(3, 4) # → 7

Active Recall 1/3

What is Python's intermediate representation between source code and the interpreter?

Under the Hood

Loading visualizer…

DNSresolving host

TCPconnecting

TLShandshake

HTTPrequesting

DSAverse

Python Execution Pipeline

Python Execution Pipeline