What is the saga pattern for distributed transactions?

def create_order():  print("  create order");  return True
def charge_card():   print("  charge card");    return True
def reserve_stock(): print("  reserve stock");  return False   # fails

def cancel_order():  print("  compensate: cancel order")
def refund_card():   print("  compensate: refund card")

# (action, compensation) pairs run in order; undo completed steps on failure.
steps = [
    (create_order, cancel_order),
    (charge_card,  refund_card),
    (reserve_stock, lambda: None),
]

done, ok = [], True
for action, compensate in steps:
    if action():
        done.append(compensate)
    else:
        ok = False
        print("step failed -> compensating", len(done), "completed step(s)")
        for c in reversed(done):       # reverse order
            c()
        break

print("saga", "committed" if ok else "rolled back")