Manual

gopy is a behavioural twin of CPython 3.14 written in Go. The interpreter parses, compiles, and runs Python source the same way CPython does. The result is the same bytecode, the same objects, the same error messages.

This manual is the user-facing slice of the site. It does not cover implementation. For that, see the CPython and gopy pillars.

What is in this manual

Page	What it covers
Install	go install and prebuilt binaries.
Run a file	gopy hello.py, exit codes, stdin scripts.
Hello, gopy	The smallest runnable program.
CLI	Every flag the binary accepts.
REPL	The interactive prompt.
Embedding	Calling the gopy VM from Go.
Status	Which Python features are wired today.
Parity	How gopy is held to CPython behaviour.

A 30 second tour

hello.py

def fizzbuzz(n):
    for i in range(1, n + 1):
        if i % 15 == 0:
            print("FizzBuzz")
        elif i % 3 == 0:
            print("Fizz")
        elif i % 5 == 0:
            print("Buzz")
        else:
            print(i)

fizzbuzz(15)

$ gopy hello.py
1
2
Fizz
4
Buzz
Fizz
7
8
Fizz
Buzz
11
Fizz
13
14
FizzBuzz

Pipe gopy -d hello.py to print the bytecode listing, or GOPY_TRACE_SPECIALIZER=1 gopy hello.py to watch the adaptive specializer in action.