goto.md

@activate_goto
def f():
    x = 0
    print('Hello World')
    x += 1
    if x > 10:
        goto_8
    goto_2

    return x

---

$ python goto.py
Hello World
Hello World
Hello World
Hello World
Hello World
Hello World
Hello World
Hello World
Hello World
Hello World
Hello World
11

goto.py

from bytecode import Bytecode, Instr, Label

def activate_goto(f):
    bytecode = Bytecode.from_code(f.__code__)

    # Map line numbers to a label to the start of that line.
    line_mapping = {}
    for i, instr in enumerate(bytecode):
        if not isinstance(instr, Instr):
            continue

        line_number = instr.lineno - bytecode.first_lineno - 1
        if line_number not in line_mapping:
            label = Label()
            bytecode.insert(i, label)
            line_mapping[line_number] = label

    for i, instr in enumerate(bytecode):
        if not isinstance(instr, Instr) or instr.name != 'LOAD_GLOBAL':
            continue
        if not instr.arg.startswith("goto"):
            continue

        target_line = int(instr.arg.replace("goto_", ""))
        target_label = line_mapping[target_line]

        instr.set('JUMP_ABSOLUTE', target_label)
        # Set the next instruction (POP_TOP) to be a no-op
        bytecode[i + 1].set('NOP')

    new_code = bytecode.to_code()
    f.__code__ = new_code
    return f


@activate_goto
def f():
    x = 0
    print('Hello World')
    x += 1
    if x > 10:
        goto_8
    goto_2

    return x


if __name__ == '__main__':
    print(f())